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PubMed1994

Alcohol dehydrogenase of class IV (sigma sigma-ADH) from human stomach. cDNA sequence and structure/function relationships.

Human stomach mucosa contains a characteristic alcohol dehydrogenase (ADH) enzyme, sigma sigma-ADH. Its cDNA has been cloned from a human stomach library and sequenced. The deduced amino acid sequence shows 59-70% identities with the other human ADH classes, demonstrating that the stomach enzyme represents a distinct structure, constituting class IV, coded by a separate gene, ADH7. The amino acid identity with the rat stomach class IV ADH is 88%, which is intermediate between constant and variable dehydrogenases. This value reflects higher conservation than for the classical liver enzymes of class I, compatible with a separate functional significance of the class IV enzyme. Its enzymic features can be correlated with its structural characteristics. The residues lining the substrate-binding cleft are bulky and hydrophobic, similar to those of the class I enzyme; this explains the similar specificity of both classes, compatible with the origin of class IV from class I. Position 47 has Arg, in contrast to Gly in the rat class IV enzyme, but this Arg is still associated with an extremely high activity (kcat = 1510 min-1) and weak coenzyme binding (KiaNAD+ = 1.6 mM). Thus, the strong interaction with coenzyme imposed by Arg47 in class I is probably compensated for in class IV by changes that may negatively affect coenzyme binding: Glu230, His271, Asn260, Asn261, Asn363. The still higher activity and weaker coenzyme binding of rat class IV (kcat = 2600 min-1, KiaNAD = 4 mM) can be correlated to the exchanges to Gly47, Gln230 and Tyr363. An important change at position 294, with Val in human and Ala in rat class IV, is probably responsible for the dramatic difference in Km values for ethanol between human (37 mM) and rat (2.4 M) class IV enzymes.

Alcohol Dehydrogenase↗

PubMed1997

Characterization of a class II pilin expression locus from Neisseria meningitidis: evidence for increased diversity among pilin genes in pathogenic Neisseria species.

Strains of Neisseria meningitidis elaborate one of two classes of pili. Meningococcal class I pili have many features in common with pili produced by N. gonorrhoeae, including the ability to bind monoclonal antibody SM1 and a common gene and protein structure consisting of conserved, semivariable, and hypervariable regions. Class II pili are SM1 nonreactive and display smaller subunit molecular weights than do gonococcal or meningococcal class I pili. In this study, we have determined the N-terminal amino acid sequence for class II pilin and isolated the expression locus encoding class II pilin from N. meningitidis FAM18. Meningococcal class II pilin displays features typical of type IV pili and shares extensive amino acid identity with the N-terminal conserved regions of other neisserial pilin proteins. However, the deduced class II pilin sequence displays several unique features compared with previously reported meningococcal class I and gonococcal pilin sequences. Class II pilin lacks several conserved peptide regions found within the semivariable and hypervariable regions of other neisserial pilins and displays a large deletion in a hypervariable region of the protein believed to be exposed on the pilus face in gonococcal pili. DNA sequence comparisons within all three regions of the coding sequence also suggest that the meningococcal class II pilin gene is the most dissimilar of the three types of neisserial pilE loci. Additionally, the class II locus fails to display flanking-sequence homology to class I and gonococcal genes and lacks a downstream Sma/Cla repeat sequence, a feature present in all other neisserial pilin genes examined to date. These data indicate meningococcal class II pili represent a structurally distinct class of pili and suggest that relationships among pilin genes in pathogenic Neisseria do not necessarily follow species boundaries.

Amino Acid Sequence↗

PubMed2002

The formation of linked perceptual classes.

Multiple-exemplar training with stimuli in four domains induced two new fill-based (A1' and A2') and satellite-image-based (B1' and B2') perceptual classes. Conditional discriminations were established between the endpoints of the A1' and B1' classes as well as the A2' and B2' classes. The emergence of linked perceptual classes was evaluated by the performances occasioned by nine cross-class probes that contained fill variants as samples and satellite variants as comparisons, along with nine other cross-class probes that consisted of satellite variants as samples and fill variants as comparisons. The 18 probes were first presented serially and then concurrently. Class-consistent responding indicated the emergence of linked perceptual classes. Of the linked perceptual classes, 70% emerged during the initial serial test. An additional 20% of the linked perceptual classes emerged during the subsequently presented concurrent test block. Thus, linked perceptual classes emerged on an immediate or delayed basis. Linked perceptual classes, then, share structural and fuctional similarities with equivalence classes, generalized equivalence classes, cross-modal classes, and complex maturally occurring categories, and may clarify processes such as intersensory perception.

Adolescent↗

PubMed2005

The effect of test schedules on the formation of linked perceptual classes.

After training conditional discriminations among selected stimuli from two perceptual classes, the emergence of novel relations involving other members of both classes was assessed using cross-class probes. The cross-class probes were presented using one of four different testing schedules. In the 2/9 test, nine different probes were presented in each of two test blocks. In the 6/3 test, three different probes were presented in each of six test blocks. In the 18/1-RND test, each of the 18 cross-class probes was presented in separate test blocks. In the 2/9 and 6/3 tests, the cross-class probes were presented in a randomized order within test block. In the 18/1-RND test, the cross-class probes were presented in a randomized sequence. In the 18/1-PRGM test, however, the cross-class probes were presented in a programmed order (i.e., the values of the stimuli in each cross-class probe were changed systematically in the succession of probe presentations). About 55% of the linked perceptual classes emerged during the 2/9, 6/3, and 18/1-RND tests. Thus the number of different probes in a test block did not influence the emergence of classes as long as the probes were presented in a random order. Virtually all classes emerged during the 18/1-PRGM test. Thus at least one ordered introduction of different cross probes resulted in the reliable emergence of linked perceptual classes. Mechanisms responsible for linked perceptual class formation are discussed along with the relation of these classes to other complex categories.

Computers↗

PubMed1999

Assessment of distribution of CD34 epitope classes in fresh and cryopreserved peripheral blood progenitor cells and acute myeloid leukemic blasts.

BACKGROUND AND OBJECTIVE: So far several reports have described changes in the expression of surface antigens in progenitor cells and blasts following cryopreservation. However, there are no data on the effects of cryopreservation on the expression of the three CD34 epitope classes, and on their relationship with the clonogenic capacity of PBPC collected by leukapheresis. DESIGN AND METHODS: In order to analyze the effects of freezing/thawing procedures (Eth 80C storage for 3 months) and use of dimethylsulfoxide (DMSO) on the immunophenotype profile and colony production of peripheral blood progenitor cells (PBPC) in apheresis products derived from 20 patients with stage 0-III non-Hodgkin's lymphoma (nHL), a flow cytometry study was undertaken using different CD34 monoclonal antibodies (MoAbs) capable of recognizing the 3 epitope classes of CD34 molecule (class III: HPCA-2/FITC, HPCA-2/PE, 581/FITC, 581/PE; class II: Q-Bend 10/PE; class I: ICH3/PE, BI3C5-PE, Immu-133-PE). CD34 epitope expression was also analyzed in thawed CD34+ blasts obtained from 14 patients with acute myeloid leukemia (AML), who were analyzed using a larger number (#17) of CD34 epitope class I, II, and III reactive MoAbs. RESULTS: Under our experimental conditions it was found that class III and class II CD34 epitopes (differentially resistant to enzymatic cleavage with neuraminidase, chymopapain and glycoprotease) are better preserved than class I epitope Eth sensitive to degradation Eth after cell exposure to cryoprotectant DMSO and the freezing- thawing procedures. Results further showed a concomitant decrease in class I CD34+ counts and in BFU-E colony production. A significant increase in CD34 antigen expression levels (i.e. antibody binding capacity, ABC) by cryopreserved cells stained with CD34 epitope class III, and class II reactive MoAbs was also documented, while no changes after cryopreservation were noted using class I-reactive MoAbs. The slight increase in the percentage of CD34+ cells detected after frozen storage was correlated to a concomitant decrease in the number of more mature myeloid cells (CD15+, CD13+, CD33+). Compared to pre-cryopreservation values, a slight reduction in class I CD34 epitope expression was also found in thawed CD34+ AML blasts. INTERPRETATION AND CONCLUSIONS: As far as the reduction of class I CD34 epitope is concerned, it may be hypothesized that the freezing procedure, use of DMSO, and/or lysis methodology may either damage a CD34 subset, or induce distinct alterations of the CD34 glycoprotein, possibly determining a reduction in their immunoreactivity with some CD34 MoAbs. In conclusion, this study has shown that exposure to the cryoprotectant DMSO and the freezing/thawing procedures modifies the distribution of CD34 epitopes as well as the clonogenic capacity of PBPCs from nHL patients, and CD34+ blasts from AML. These findings need to considered when selecting CD34 MoAbs for enumeration and positive selection of stem/progenitor cells for research and clinical purposes.

Acute Disease↗

PubMed1992

The loss of class II MHC antigen expression by ras-transformed murine fibroblasts passaged as tumours correlates with increased tumorigenicity but is not mediated by T cells.

In several murine tumour systems, expression of class II major histocompatibility complex (MHC) antigens by tumour cells, either constitutive or inducible, correlates with reduced tumorigenicity as compared with equivalent class-II-negative cells, and CD4 phenotype T cells together with interferon gamma (which induces the expression of class II) may be involved in the control of the proliferation of class-II-expressing tumours. This implies a potential T-cell-mediated selection pressure against class II expression. To test this possibility, we have repeatedly passaged as tumours in euthymic, syngeneic mice ras-transformed murine fibroblast lines, which are class-II-inducible, to determine whether class-II-non-inducible variants are selected. We examined the expression of both class I and class II antigen in tumour cells re-established in vitro. It was found that the inducibility of class II, but not class I, expression rapidly diminished, correlating with augmented tumorigenicity. However, this loss of class II inducibility occurred in athymic as well as euthymic mice. Therefore, despite the fact that the tumorigenicity of these lines is augmented in euthymic mice depleted of CD4 T cells or interferon gamma, we found no evidence of T-cell-mediated selection against class II expression. The loss of class II expression observed must be due to mechanisms other than immune selection. The possibility that this might result from other soluble factors modulating the response to interferon gamma in vivo is discussed.

Animals↗

PubMed2002

Expression of invariant chain can cause an allele-dependent increase in the surface expression of MHC class I molecules.

Invariant chain (Ii) has been shown to play a significant part in the assembly of MHC class II molecules. Ii also binds to MHC class I, although it is not known when this first occurs or whether it can affect class I assembly. Our examination of lysates of L(d)-transfected T2 cells showed that Ii bound intracellularly to folded, but not to open, forms of MHC class I. Furthermore, addition of peptides to the lysates dissociated Ii from the Ii-folded MHC class I complex. Thus, unlike other known chaperones, Ii associates only with folded, peptide-free class I molecules. To determine whether Ii can affect MHC class I transport and surface expression, we used both wild-type Ii and a mutant Ii that lacked the endosomal targeting sequence. Neither Ii nor Ii(Delta 20) increased the rate of MHC class I migration; however, Ii and (to a greater extent) Ii(Delta 20) increased cell surface expression of MHC class I. In HeLa cells, this effect was allele-specific, affecting HLA-A28 more than -B75. Ii also increased the surface expression of K(b) more than D(b) on Panc02 pancreatic adenocarcinoma cells. Neither form of Ii was detectable at the cell surface with MHC class I, indicating that Ii had exercised its effect on class I intracellularly. In total, these data suggest that Ii can bind peptide-free folded class I/beta(2)m heterodimers, but not open MHC class I heavy chains, in the endoplasmic reticulum, and that Ii can facilitate the surface expression of the MHC class I molecule.

Alleles↗

PubMed1997

Longitudinal evaluation of growth changes in Class II division 1 subjects.

Longitudinal records from the Ohio State University Growth Study were used to compare the skeletal growth changes between Class II division 1 and Class I female subjects between ages 7 and 14. Tensor analysis was used to determine the yearly growth rate and direction. No significant difference was found in cranial base dimension between the Class I and Class II subjects. In Class II subjects, the maxilla (S-N-A) was found to be normally related to the cranial base. However, mandibular position (S-N-B and S-N-Pog) was found to be significantly more retrusive in Class II when compared with Class I subjects. Mandibular length (Ar-Gn) and corpus length (Go-Gn) were found to be shorter in Class II subjects. The ratio of PFH to AFH was found to be smaller in Class II subjects. This is particularly apparent during the pubertal growth period. The y-axis and mandibular plane angle were more open in Class II subjects which also contributed to the retrusive position of the mandible. Maxillo-mandibular difference (A-N-B) between Class I and II subjects was present at age 7 and persisted through puberty, maintaining a greater angle of convexity (A-N-Pg) in Class II subjects. These results suggest that Class II malocclusion can be detected early. The majority of the Class II cases showed mandibular skeletal retrusion or a combination of horizontal and vertical abnormalities of the mandible rather than maxillary protrusion. These skeletal differences remain through puberty without orthodontic intervention. Individual variations were found within each type of malocclusion.

Adolescent↗

PubMed1994

Specific inhibition of HLA class I and II antibodies by soluble antigens--a method for the identification of antibody specificity in sera from alloimmunized individuals.

HLA class I and II antigens were purified to be used for the determination of the specificity of lymphocyte reactive antibodies in renal transplant patients. Purification of HLA antigens was achieved by affinity chromatography using rabbit antibodies directed to human beta 2 microglobulin, W6/32 antibodies that recognize a nonpolymorphic determinant on HLA class I molecules, and BU25 monoclonal antibodies directed to a monomorphic determinant on HLA class II molecules. Pooled platelets and spleen lymphocytes from a large number of donors were used as a source of class I and II antigens. HLA antigen preparations, highly enriched as shown in Western blot experiments, were obtained that caused a dose-dependent inhibition of the binding as well as of the cytotoxicity of W6/32 and BU25 antibodies. The HLA class I preparation did not inhibit the binding of monoclonal antibodies to T or B cell-specific surface markers or to HLA class II antigens. Similar kinds of results were obtained with the HLA class II antigen preparation, which only specifically blocked the class II antibody binding. The antigen preparations were tested for their ability to block binding of antibodies in sera from alloimmunized patients. In order to avoid complications by soluble HLA antigens, all sera were absorbed in ELISA plates coated with anti-class I and anti-class II monoclonal antibodies. The HLA class I and class II antigen preparations were found to be HLA-specific. All data were compared with the conventional method to determine HLA specificity--i.e., specific blocking of class I and class II reactivity using monoclonal antibodies and unabsorbed sera. Soluble HLA antigens, added directly to mixtures of patient sera and lymphocytes used in the cytotoxicity or binding tests, can therefore be used for determination of the presence of HLA antibodies in sera of alloimmunized patients.

Antibodies, Monoclonal↗

PubMed1995

The interaction of beta 2-microglobulin (beta 2m) with mouse class I major histocompatibility antigens and its ability to support peptide binding. A comparison of human and mouse beta 2m.

The function of major histocompatibility complex (MHC) class I molecules is to sample peptides derived from intracellular proteins and to present these peptides to CD8+ cytotoxic T lymphocytes. In this paper, biochemical assays addressing MHC class I binding of both peptide and beta 2-microglobulin (beta 2m) have been used to examine the assembly of the trimolecular MHC class I/beta 2m/peptide complex. Recombinant human beta 2m and mouse beta 2ma have been generated to compare the binding of the two beta 2m to mouse class I. It is frequently assumed that human beta 2m binds to mouse class I heavy chain with a much higher affinity than mouse beta 2m itself. We find that human beta 2m only binds to mouse class I heavy chain with slightly (about 3-fold) higher affinity than mouse beta 2m. In addition, we compared the effect of the two beta 2m upon peptide binding to mouse class I. The ability of human beta 2m to support peptide binding correlated well with its ability to saturate mouse class I heavy chains. Surprisingly, mouse beta 2m only facilitated peptide binding when mouse beta 2m was used in excess (about 20-fold) of what was needed to saturate the class I heavy chains. The inefficiency of mouse beta 2m to support peptide binding could not be attributed to a reduced affinity of mouse beta 2m/MHC class I complexes for peptides or to a reduction in the fraction of mouse beta 2m/MHC class I molecules participating in peptide binding. We have previously shown that only a minor fraction of class I molecules are involved in peptide binding, whereas most of class I molecules are involved in beta 2m binding. We propose that mouse beta 2m interacts with the minor peptide binding (i.e. the "empty") fraction with a lower affinity than human beta 2m does, whereas mouse and human beta 2m interact with the major peptide-occupied fraction with almost similar affinities. This would explain why mouse beta 2m is less efficient than human beta 2m in generating the peptide binding moiety, and identifies the empty MHC class I heavy chain as the molecule that binds human beta 2m preferentially.

Amino Acid Sequence↗

PubMed1993

Differential expression of bovine MHC class II antigens identified by monoclonal antibodies.

Four monoclonal antibodies (mAbs), UC-A4, UC-D3, UC-H9, and IL-A21, specific for bovine major histocompatibility complex class II proteins are described. Sequential immunoprecipitation experiments using biotin-labeled peripheral blood mononuclear cells suggested, but did not conclusively establish, that each of these antibodies recognized a different epitope. The epitope identified by IL-A21 appeared to be common to all of the class II proteins precipitated by the four mAbs, and UC-D3 and UC-H9 each appeared to react with distinct epitopes on separate subsets of these class II proteins. Monoclonal antibody UC-A4 appeared to identify an epitope on a subset of the class II molecules identified by UC-H9. Differences found in the expression by lymphoid cells of class II proteins identified by the four mAbs were indicative of each mAb recognizing a different epitope. UC-H9 and IL-A21 class II proteins were detected on all surface immunoglobulin (S'Ig) positive cells in peripheral blood, but UC-A4 and UC-D3 class II proteins were not. Expression of UC-A4 class II proteins, detected at low density on a strikingly reduced number of S'Ig+ cells from the blood of some bovine leukosis virus-infected cattle, could be increased by culturing these B cells with lipopolysaccharide. All peripheral blood monocytes expressed UC-H9 and IL-A21 class II proteins, but only a proportion of monocytes expressed detectable UC-A4 and UC-D3 class II proteins. Almost all mitogen-stimulated BoCD4+ and BoCD8+ T cells expressed UC-H9 and IL-A21 class II proteins, whereas fewer stimulated T cells of both subsets expressed UC-A4 and UC-D3 class II proteins. All gamma/delta receptor (gamma/delta R) T cells expressed UC-D3, UC-H9, and IL-A21 class II proteins, but no cells (of gamma/delta R+ or CD4+/CD2+ phenotype) from gamma/delta R+ T cell-enriched cultures expressed UC-A4 class II proteins.

Animals↗

PubMed1990

Membrane-bound and water-soluble nonclassical class I MHC antigens on rat placenta.

We have used mouse monoclonal antibodies to different determinants on rat class I major histocompatibility complex (MHC) antigens in order to identify water-soluble and membrane-bound nonclassical (i. e., non-RT1.A) class I MHC antigens on the spongiotrophoblast and labyrinthine trophoblast of rat placenta. Initial immunohistological studies with monoclonal antibodies reacting with a determinant restricted to classical (RT1.A) rat class I antigens confirmed the presence of these antigens on spongiothrophoblast, but not on labyrinthine trophoblast. Staining with another monoclonal antibody, which reacts with both classical and at least some nonclassical rat class I antigens, gave strong staining of both the labyrinthine and spongiotrophoblast. To distinguish membrane-bound from water-soluble class I molecules, quantitative absorption analyses were carried out using both placental cell membranes and ultracentrifuged aqueous extracts of placenta. The aqueous placental extract had no absorptive capacity for the RT1.A-specific antibodies, but it had very strong absorptive capacity for the more broadly reactive antibody. This strongly suggests the presence of large quantities of a soluble nonclassical class I MHC antigen in rat placenta. The placental cell membranes had four to fivefold greater absorptive capacity for the broadly reactive antibody when compared to the antibodies to classical class I antigens, a result that was consistent with the presence of membrane-bound nonclassical class I antigens on rat placenta. The membrane-bound nonclassical class I antigen was purified from detergent extracts of DA rat placental membranes using monoclonal antibody affinity and lentil lectin affinity chromatography. The putative nonclassical class I antigen had a heavy chain of Mr 43,000, which is 2000 smaller than the classical (RT1.A) class I antigen. N-terminal amino acid sequence analysis demonstrated that the nonclassical placental antigen differed at three amino acid residues from the classical RT1.A class I molecule and also from the Q10-like class I molecule of the DA strain. It differed also from the pAR 1.5 cDNA sequence, the only full-length rat class I DNA sequence available so far.

Amino Acid Sequence↗

PubMed1990

Evolution of the MHC: antigenicity and unusual tissue distribution of Xenopus (frog) class II molecules.

Antibodies that recognize Xenopus class II molecules have been developed. Mouse monoclonal antibodies were prepared by immunizing BALB/c mice with frog MHC antigens that had been partially purified with alloantisera, and by immunizing mouse spleen cells in vitro with activated Xenopus T lymphocytes. In addition, five mouse monoclonal antibodies specific for human class II antigens were found to cross-react with Xenopus class II antigens. A.TH mice, which do not express E class II molecules, always produce immunoprecipitating antibodies reactive with frog class II molecules after immunization with frog lymphocytes; other mouse strains rarely produce such antibodies. Two of the monoclonal antibodies raised against frog class II molecules recognize the denatured class II beta chain on Western blots, and the other three appear to recognize only the class II heterodimeric complex. The antibodies display differential reactivity with the allelic class II products of Xenopus. The monoclonal antibodies react with all adult lymphocytes in the spleen and peripheral blood, T cells and B cells having equivalent levels of class II antigens per cell. Class II molecules are "differentiation antigens" on adult thymocytes as the expression is greatest on the mature medullary population. The number of class II molecules/lymphocyte increases after culturing in medium containing fetal bovine serum. Sequential immunoprecipitation and isoelectric focusing experiments have shown that cell surface class II molecules immunoprecipitated with the monoclonal antibodies are the same as those immunoprecipitated with the cross-reactive antiserum specific for DR antigens which was previously used to identify frog class II molecules.

Animals↗

PubMed1994

Variation in expression of MHC class II antigens on horse lymphocytes determined by MHC haplotype.

A panel of monoclonal antibodies was used to characterize the expression of equine Major Histocompatibility Complex (MHC) class II antigens on lymphocytes of horses of different MHC types. MHC class II antigen expression was compared between adult horses and foals, and the level of expression of MHC class II antigens on horse T cell subpopulations was also determined. Peripheral blood lymphocytes (PBL) from young and adult healthy horses of different MHC haplotypes were labeled with the antibodies and assayed by single- and two-color immunofluorescence flow cytometry. A variation in the expression of equine MHC class II antigens on PBL was identified that was determined by MHC haplotype. Both young and old animals carrying the MHC class II haplotype D3 expressed lower levels of MHC class II antigens on their PBL than did horses of other MHC class II types. D3 heterozygotes had an intermediate level of expression. Neonates and foals of any MHC haplotype had lower levels of expression of MHC class II antigens than did adults. MHC class II antigens were identified on surface immunoglobulin positive (sIg+) B cells as well as on T cells, with the B cells staining brightest. Dual staining for MHC class II antigens and markers for equine T cell subsets demonstrated that both EqCD4+ and EqCD8+ T cells expressed MHC class II molecules. These results suggest that the relatively low levels of MHC class II antigen expression on foal and neonate lymphocytes may be developmentally regulated, and not determined by environmental factors. The cause of the low expression of MHC class II antigens linked to the MHC class II haplotype D3 is not known, but it appears to reflect a decreased expression by all lymphocyte subpopulations.

Animals↗

PubMed1998

Mandibular changes in persons with untreated and treated Class II division 1 malocclusion.

The growth potential of individuals with Class II malocclusions is of interest to the practicing orthodontist because such malocclusions constitute a significant percentage of cases. The purpose of this study was to evaluate on cross-sectional and longitudinal bases the changes in mandibular length and relationship and maxillary-mandibular relationships in untreated Class II subjects from deciduous to permanent dentition and also to evaluate the effects of orthodontic treatment, with and without the extraction of first premolars, on these relationships. Class II samples were compared with matched normal, untreated individuals. The Class II division 1 (Class II/1) untreated sample comprised 30 subjects, 15 males and 15 females. Each subject had a complete set of data at three stages of dental development-namely, Stage I, after the completion of eruption of the deciduous dentition; Stage II, at the time when the permanent first molars and most of the incisors have erupted (i.e., in mixed dentition); and Stage III, at the completion of eruption of the permanent dentition, excluding third molars. The Class II treated sample comprised 44 subjects (21 males, 23 females) treated with four first-premolar extractions and 47 subjects (20 males, 27 females) treated without extraction. Treatment was accomplished with the use of an edgewise appliance, appropriate extraoral traction, and Class II elastics. The extraction decision was based mainly on the presence of crowding and profile consideration. Records on 35 normal subjects (20 males, 15 females) were available from the Iowa Longitudinal Facial Growth Study. Cephalograms for the normal individuals were matched to the corresponding ages of the Class II cases. With regard to these findings, few consistent differences were noted between the untreated Class II/1 and normal subjects on cross-sectional comparisons. The differences in mandibular length and position were more evident in the early stages of development than at later stages. Longitudinal comparisons of growth profiles indicated that the growth trends were essentially similar between the untreated Class II/1 and normal subjects in the various parameters compared. The comparisons of growth magnitude indicated the presence of greater skeletal facial convexity in the untreated Class II/1 subjects, accompanied by a tendency for a more retruded mandible. Initial comparisons between the Class II/1 treated groups and normal subjects indicated that the Class II/1 malocclusions were associated with a larger overjet, deeper overbite, and greater ANB angle. After a 5-year treatment and observation period, an overall "normalization" in the mandibular and maxillary-mandibular skeletal relationships was noted in the treated Class II/1 subjects in both the extraction and the nonextraction groups compared with normal subjects. The changes were more pronounced in the extraction group.

Adolescent↗

PubMed1999

Evidence of increasing coronary heart disease mortality among black men of lower social class.

PURPOSE: Few data are available to examine coronary heart disease (CHD) mortality trends by social class in the United States, in contrast to ample data and well-documented social class disparities in CHD in Europe. In addition, previous analyses of U.S. national data indicated that the rate of decline in CHD mortality slowed substantially for blacks in the 1980s. Using a recently published method for calculating mortality rates by social class, we examined trends in CHD mortality for black men and white men aged 35-54 in North Carolina from 1984 to 1993. METHODS: Men were assigned to one of four social classes: primary white collar (I), secondary white collar (II), primary blue collar (III), or secondary blue collar (IV), based on usual occupation as recorded on the death certificate. Population denominators for each social class were constructed using data from census Public Use Microdata Sample files. Average annual percent change in mortality rates for each race-social class group was derived from linear regression of the log-transformed age-adjusted rates. RESULTS: For black men, CHD mortality increased by 18% in social class II, by 2% in social class III, and by 6% in social class IV over the 10-year study period. In contrast, CHD mortality decreased by 33% for black men in social class I (the highest class). CHD mortality declined for all white men, with the greatest decline in social class I and the least decline in social class IV. CONCLUSIONS: These results suggest that CHD prevention efforts have not benefited black men of lower social class, and that public health programs need to be targeted to these men.

Adult↗

PubMed1996

Glu227-->Lys substitution in the acidic loop of major histocompatibility complex class I alpha 3 domain distinguishes low avidity CD8 coreceptor and avidity-enhanced CD8 accessory functions.

Cytotoxic T lymphocyte (CTL) activation requires specific T cell receptor (TCR)-class I major histocompatibility complex (MHC) antigen complex interactions as well as the participation of coreceptor or accessory molecules on the surface of CTL. CD8 can serve as a coreceptor in that it binds to the same MHC class I molecules as the TCR to facilitate efficient TCR signaling. In addition, CD8 can be "activated" by TCR stimulation to bind to class I molecules with high avidity, including class I not recognized by the TCR as antigenic complexes (non-antigen [Ag] class I), to augment CTL responses and thus serve an accessory molecule function. A Glu/Asp227-->Lys substitution in the class I alpha 3 domain acidic loop abrogates lysis of target cells expressing these mutant molecules by alloreactive CD8-dependent CTL. Lack of response is attributed to the destruction of the CD8 binding site in the alpha 3 domain which is likely to disrupt CD8 coreceptor function. The relative importance of the class I alpha 3 domain acidic loop Glu227 in coreceptor as opposed to accessory functions of CD8 is unclear. To address this issue, we examined CTL adhesion and degranulation in response to immobilized class I-peptide complexes formed in vitro from antigenic peptides and purified class I molecules containing wild-type or Glu227-->Lys substituted alpha 3 domains. The alpha 3 domain mutant class I-peptide complexes were bound by CTL and triggered degranulation, however to much lower levels than wild-type class I-peptide complexes. In further experiments, it is directly demonstrated that the alpha 3 domain mutant class I molecules, which lack the Glu227 CD8 binding site, still serve as TCR-activated, avidity-enhanced CD8 accessory ligands. However, mutant class I peptide Ag complexes failed to effectively serve as CD8 coreceptor ligands to initiate TCR-dependent signals required to induce avidity-enhanced CD8 binding to coimmobilized non-Ag class I molecules. Thus the Glu227-->Lys mutation effectively distinguishes CD8 coreceptor and avidity-enhanced CD8 accessory functions.

Binding Sites↗

PubMed1999

Absence of spontaneous central nervous system remyelination in class II-deficient mice infected with Theiler's virus.

We previously showed that Theiler's murine encephalomyelitis virus (TMEV)-infected major histocompatibility complex (MHC) class II-deficient mice develop both demyelination and neurologic deficits, whereas MHC class I-deficient mice develop demyelination but no neurologic deficits. The absence of neurologic deficits in the class I-deficient mice was associated with preserved sodium channel densities in demyelinated lesions, a relative preservation of axons, and extensive spontaneous remyelination. In this study, we investigated whether TMEV-infected class II-deficient mice, which have an identical genetic background (C57BL/6 x 129) as the class I-deficient mice, have preserved axons and spontaneous myelin repair following chronic TMEV-infection. Both class I- and class II-deficient mice showed similar extents of demyelination of the spinal cord white matter 4 months after TMEV infection. However, the class I-deficient mice demonstrated remyelination by oligodendrocytes, whereas class II-deficient mice showed minimal if any myelin repair. Demyelinated lesions, characterized by inflammatory infiltrates in both mutants, revealed disruption of axons in class II- but not class I-deficient mice. Further characterization revealed that even though class II-deficient mice lacked TMEV-specific IgG, they had virus-specific IgM, which, however, did not neutralize TMEV in vitro. In addition, class II-deficient mice developed TMEV-specific cytotoxic T-lymphocytes in the CNS during the acute (7 days) disease, but these cytotoxic lymphocytes were not present in the chronic stage of disease, despite a high titer of infectious virus throughout the disease. We envision that the presence of demyelination, high virus titer, absence of remyelination, and axonal disruption in chronically infected class II-deficient mice contributes to the development of paralytic disease.

Acute Disease↗