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PubMed1992

Evolutionary origin of the class A and class C beta-lactamases.

The protein sequences of 18 class A beta-lactamases and 2 class C beta-lactamases were analyzed to produce a rooted phylogenetic tree using the DD peptidase of Streptomyces R61 as an outgroup. This tree supports the penicillin-binding proteins as the most likely candidate for the ancestoral origin of the class A and class C beta-lactamases, these proteins diverging from a common evolutionary origin close to the DD peptidase. The actinomycetes are clearly shown as the origin of the class A beta-lactamases found in other non-actinomycete species. The tree also divides the beta-lactamases from the Streptomyces into two subgroups. One subgroup is closer to the DD peptidase root. The other Streptomyces subgroup shares a common branch point with the rest of the class A beta-lactamases, showing this subgroup as the origin of the non-actinomycete class A beta-lactamases. The non-actinomycete class A beta-lactamase phylogenetic tree suggests a spread of these beta-lactamases by horizontal transfer from the Streptomyces into the non-actinomycete gram-positive bacteria and thence into the gram-negative bacteria. The phylogenetic tree of the Streptomyces class A beta-lactamases supports the possibility that horizontal transfer of class A beta-lactamases occurred within the Streptomyces.

Amino Acid Sequence↗

PubMed1988

Interferon-induced expression of class II major histocompatibility antigens in the major histocompatibility complex (MHC) class II deficiency syndrome.

Class II antigens encoded by genes of the major histocompatibility complex (MHC) are expressed by a variety of cell types and have a vital role in the cellular interactions required for an effective immune response. We have analyzed the regulation of HLA-DR, DP, and DQ class II antigen expression on cells of different lineage from an immunodeficient patient with the MHC class II deficiency syndrome. T and B lymphocytes, monocytes, and fibroblasts, which initially expressed no class II antigens, were treated with inductive stimuli that normally lead to enhanced expression of class II antigens. Monocytes, but not fibroblasts, cultured for 48-96 hr in the presence of recombinant gamma interferon expressed all three types of class II antigens. In contrast, T lymphocytes did not express class II antigens following their exposure to a variety of stimuli, including activation with phytohemagglutinin and culture in the presence of interleukin-2, transformation by the retrovirus HTLV-1 or HTLV-2, or exposure to the demethylating agent 5-azacytidine. Similarly, class II antigens were not induced on B cells by cross-linkage of surface immunoglobulin molecules with anti-mu, exposure to Epstein-Barr virus, or treatment with soluble factors secreted by activated T cells. These results demonstrate that the regulation of class II MHC antigen expression by monocytes and lymphocytes is dissimilar and suggest that different regulatory genes are involved in the control of class II antigen expression by cells of different lineage.

Adult↗

PubMed1984

Domain structures and molecular evolution of class I and class II major histocompatibility gene complex (MHC) products deduced from amino acid and nucleotide sequence homologies.

Domain structures of class I and class II MHC products were analyzed from a viewpoint of amino acid and nucleotide sequence homologies. Alignment statistics revealed that class I (transplantation) antigen H chains consist of four mutually homologous domains, and that class II (HLA-DR) antigen beta and alpha chains are both composed of three mutually homologous ones. The N-terminal three and two domains of class I and class II (both beta and alpha) gene products, respectively, all of which being approximately 90 residues long, were concluded to be homologous to beta2-microglobulin (beta2M). The membrane-embedded C-terminal shorter domains of these MHC products were also found to be homologous to one another and to the third domain of class I H chains. Class I H chains were found to be more closely related to class II alpha chains than to class II beta chains. Based on these findings, an exon duplication history from a common ancestral gene encoding a beta2M-like primodial protein of one-domain-length up to the contemporary MHC products was proposed.

Amino Acid Sequence↗

PubMed1988

Effect of interferon-gamma and tumor necrosis factor on the expression of class I and class II major histocompatibility molecules by cultured human umbilical vein endothelial cells.

The expression of class I and class II major histocompatibility complex (MHC) molecules on the surface of cultured human umbilical vein endothelial cells (HUVEC) incubated with alpha tumor necrosis factor (TNF) or interferon-gamma (IFN-gamma) was determined by fluorescence flow cytometry. HUVEC were stained with fluorescein conjugated monoclonal antibodies (MoAbs) directed against monomorphic determinants of class I MHC molecules, HLA-A, B alpha chain (HLA-alpha) and beta-2-microglobulin (B2m), and class II MHC molecules, HLA-DR and HLA-DQ. HUVEC exposed to TNF for 96 hr increase their expression of class I MHC molecules two- to fourfold. Similarly, IFN-gamma increases the expression of class I MHC molecules two- to fivefold. No induction of HLA-DR or HLA-DQ was seen following exposure to TNF. IFN-gamma induces the appearance and markedly increases the expression of HLA-DR following 96 hr incubation. HLA-DQ was also induced by IFN-gamma but to a much lesser extent. TNF in combination with IFN-gamma enhances HUVEC expression of HLA-alpha, B2m, and HLA-DQ greater than that observed with either mediator alone. TNF and IFN-gamma reduced HUVEC expression of HLA-DR below the level observed with IFN-gamma alone. Indomethacin (INDO) does not effect expression of HUVEC class I or class II MHC molecules induced by TNF, IFN-gamma, or the combination of these mediators. These immune mediators produce unique and common effects on HUVEC, and therefore may act by at least two separate mechanisms, independent of the cyclooxygenase pathway, which regulate HUVEC expression of class I and class II MHC surface molecules.

Antibodies, Monoclonal↗

PubMed1992

Cell-cell interaction in graft rejection responses: induction of anti-allo-class I H-2 tolerance is prevented by immune responses against allo-class II H-2 antigens coexpressed on tolerogen.

The intravenous sensitization of C57BL/6 (B6) mice with class I H-2-disparate B6-C-H-2bm1 (bm1) spleen cells results in almost complete abrogation of anti-bm1 CD8+ helper (proliferative and interleukin 2-producing) T cell (Th) activities. Although an appreciable portion of CD8+ cytotoxic T lymphocyte (CTL) precursors themselves remained after this regimen, such a residual CTL activity was eliminated after the engrafting of bm1 grafts, and these grafts exhibited prolonged survival. In contrast, the intravenous sensitization with (bm1 x B6-C-H-2bm12 [bm12])F1 cells instead of bm1 cells failed to induce the prolongation of bm1 graft survival as well as bm12 and (bm1 x bm12)F1 graft survival. In the (bm1 x bm12)F1-presensitized B6 mice before as well as after the engrafting of bm1 grafts, anti-bm1 CTL responses that were comparable to or slightly stronger than those observed in unpresensitized mice were induced in the absence of anti-bm1 Th activities. bm1 graft survival was also prolonged by intravenous presensitization with a mixture of bm1 and bm12 cells but not with a mixture of bm1 and (bm1 x bm12)F1 cells. The capacity of CD4+ T cells to reject bm12 grafts was eliminated by intravenous presensitization with antigen-presenting cell (APC)-depleted bm12 spleen cells. However, intravenous presensitization with APC-depleted (bm1 x bm12)F1 cells failed to induce the prolongation of bm1 graft survival under conditions in which appreciably prolonged bm12 graft survival was induced. More surprisingly, bm1 graft survival was not prolonged even when the (bm1 x bm12)F1 cell presensitization was performed in CD4+ T cell-depleted B6 mice. This contrasted with the fact that conventional class I-disparate grafts capable of activating self Ia-restricted CD4+ as well as allo-class I-reactive CD8+ Th exhibited prolonged survival in CD4+ T cell-depleted, class I-disparate cell-presensitized mice. These results indicate that: (a) intravenous presensitization with class I- and II-disparate cells fails to reduce anti-allo-class I rejection responses that would otherwise be eliminated using only class I-disparate cells; (b) such failure is generated according to the coexpression of both classes of alloantigens on a single cell as tolerogen; and (c) allo-class II antigens coexpressed on tolerogen function to activate CD4+ as well as non-CD4+ Th leading to the generation of anti-class I effector T cell responses.

Animals↗

PubMed1986

Sequential analysis of HLA-class II antigen expression in human renal allografts. Induction of tubular class II antigens and correlation with clinical parameters.

The expression of HLA-class II antigens was assessed in 142 biopsies from 29 recipients of cadaveric renal allografts who received either short-term cyclosporine (n = 12) or azathioprine and low-dose prednisolone (n = 17). Biopsies were obtained before transplantation, routinely at days 7, 21, 90, and 365 after transplantation, and at other times as clinically indicated. Cryostat sections were labeled with monoclonal antibodies using an indirect immunoperoxidase technique. In all biopsies HLA-class II antigens were expressed on glomeruli and intertubular structures. In pretransplant biopsies proximal tubules expressed class II antigens, whereas distal tubules were always negative. After transplantation three patterns of class II expression were recognized based on renal tubular class II staining: normal, focal increased, and generalized increased expression. Sequential biopsy analysis showed fluctuating levels of expression in individual patients, which correlated with cellular infiltration and was associated with allograft rejection. 71% of biopsies obtained at day 90 from patients on conventional therapy showed increased class II expression compared with only 9% of biopsies from patients on cyclosporine immunosuppression. All patients with normal class II antigen expression in day 90 biopsies had well-functioning grafts two years after transplantation, whereas 3 of 9 with increased class II antigen expression had failed. Furthermore, all grafts failing from irreversible rejection before 90 days showed marked increase of class II antigen expression. The increased class II antigen expression in renal allografts may be merely a marker of rejection or may have a role in the augmentation of the response, either in its induction or as a target for the effector arm of the reaction.

Azathioprine↗

PubMed1990

Fracture strength of Class I versus Class II restored premolars tested at the marginal ridge. I. Standard preparations.

Two groups of maxillary premolars with Class I cavities were prepared with one marginal ridge thickness to a width of 1.0 mm. One group was restored with amalgam and the other group with composite resin. Two groups of Class II cavities also were prepared and restored with amalgam and composite resin. The teeth in the four treatment groups were subjected to a centric load at the marginal ridge until fracture occurred. A two-factor analysis of variance revealed a statistically significant difference between the class of preparation (Class I preparations were weaker than were Class II preparations) but differences in strength between restorative materials (composite resin versus amalgam) and the interaction effect (class of preparation x restorative materials) were not found to be statistically significant (alpha = .05). A Newman-Keuls sequential range test found no statistically significant differences in strength between groups (alpha = .05). Fracture patterns were observed under scanning electron microscope. Fractures extended into the enamel and into the material in the Class I composite resin, Class I amalgam, and Class II composite resin restorations. Fractures extended only into the material in Class II amalgam restorations.

Bicuspid↗

PubMed1985

HLA class-I and class-II antigen expression by human leukemic K562 cells and by Burkitt-K562 hybrids: modulation by differentiation inducers and interferon.

K562 cells, which could be regarded as pluripotent hematopoietic progenitors, are usually considered as HLA class-I and class-II-negative cells. We show here that differentiation induction (with either sodium butyrate, 12-O-tetradecanoyl-phorbol-13-acetate, or teleocidin) or recombinant alpha- or gamma-interferon (IFN) treatment resulted in the augmentation of HLA class-I antigen expression. This augmentation of HLA class-I antigens was also observed in the Burkitt X K562 hybrid cells PUTKO and DUTKO (the latter coming from two presumably HLA-A, B-negative parents). HLA class-I genes are thus functional in K562 cells. In this system, alpha- and gamma-IFN had no clear differentiating capacity, since they were not able to modulate the expression of various hematopoietic markers, as chemical differentiation inducers did. On the other hand, neither differentiation induction nor interferon treatment could induce HLA class-II antigen expression on K562 cells. These molecules could be very faintly induced in PUTKO and DUTKO hybrids, in contrast with strong HLA class-II expression on the B parental lines. Whether these results are due to "lineage infidelity" in K562 cells or whether K562 cells represent the proliferation of HLA class-I-positive class-II-negative hematopoietic cells, with active suppression of HLA class-II antigen expression, is discussed.

Burkitt Lymphoma↗

PubMed1991

Cytosolic targeting of hen egg lysozyme gives rise to a short-lived protein presented by class I but not class II major histocompatibility complex molecules.

A way to study the role of intracellular trafficking of an antigen in its presentation to T cells is to target the antigen to various cell compartments of the antigen-presenting cells (APC) and compare the nature of the complexes associating major histocompatibility complex (MHC) molecules and antigenic peptides, expressed on the cell surface. MHC class I+ and MHC class II+ mouse L fibroblasts secreting hen egg lysozyme (HELs cells) or expressing HEL in their cytosol (HELc cells) were obtained after transfection with HEL cDNA and signal sequence-deleted HEL cDNA, respectively. HEL was evidenced in both HELs- and HELc-transfected cells and the former type of transfectant secreted a large amount of HEL. However, HEL produced in the cytosol exhibited a short half-life of less than 5 min. HEL-derived peptides could not be shown biochemically either in HELc- nor in HELs-transfected cells. We then studied the capacity of these cells to present HEL to HEL-specific class I- and class II-restricted T cells. Both cell types could be recognized by the HEL-specific MHC class I-restricted CTL clones. In contrast, MHC class II-HEL peptide complexes, recognized by HEL-specific helper T cell hybridomas, could be detected on MHC class II+ HELs- but not HELc-transfected cells. In vivo experiments showed, however, that HELc-transfected cells could provide host APC with HELc-derived peptides able to associate with MHC class II molecules. This was inferred from the capacity of MHC class II-HELc-transfected cells, unable by themselves to elicit any anti-HEL antibody response, to prime syngeneic and allogeneic mice against HEL. The priming was revealed by the induction of an antibody response after a boost with an amount of HEL unable itself to elicit an antibody response.

Amino Acid Sequence↗

PubMed1995

Major histocompatibility complex class I-restricted CD8+ T cells and class II-restricted CD4+ T cells, respectively, mediate and regulate contact sensitivity to dinitrofluorobenzene.

Contact sensitivity (CS) is a form of delayed-type hypersensitivity to haptens applied epicutaneously and is thought to be mediated, like classical delayed-type hypersensitivity responses, by CD4+ T helper-1 cells. The aim of this study was to identify the effector T cells involved in CS. We studied CS to the strongly sensitizing hapten dinitrofluorobenzene (DNFB) in mice rendered deficient by homologous recombination in either major histocompatibility complex (MHC) class I, MHC class II, or both, and which exhibited deficiencies in, respectively, CD8+, CD4+, or both, T cells. MHC class I single-deficient and MHC class I/class II double-deficient mice, both of which have a drastic reduction in the number of CD8+ T cells, were unable to mount a CS response to DNFB. In contrast, both MHC class II-deficient mice and normal mice treated with an anti-CD4 monoclonal antibody (mAb) developed exaggerated and persistent responses relative to heterozygous control littermates. Furthermore, anti-CD8 mAb depletion of class II-deficient mice totally abolished their ability to mount an inflammatory response to DNFB. Removal of residual CD4+ T cells in class II-deficient mice by anti-CD4 mAb treatment did not diminish the intensity of CS. These data clearly demonstrate that class I-restricted CD8+ T cells are sufficient for the induction of CS to DNFB, and further support the idea that MHC class II-restricted CD4+ T cells down-regulate this inflammatory response.

Animals↗

PubMed1988

A molecular map of the chicken major histocompatibility complex: the class II beta genes are closely linked to the class I genes and the nucleolar organizer.

We have cloned in a cosmid vector four DNA clusters covering 320 kb of the chicken MHC (B complex), including five class II (B-L) beta genes defining two related isotypic families. Additional B complex genes have been revealed using tissue-specific cDNA probes. A cosmid fragment has been used to isolate a cDNA for a class I (B-F) transcript. This transcript, that is by far the most divergent known member of the class I gene family, hybridized to six B-F genes present in the cosmids. One of the clusters was shown to contain two rRNA transcriptional units from the nucleolar organizer region (NOR), marking the telomeric boundary of the B complex. None of the other B complex genes hybridizes to, or has the transcriptional characteristics of mammalian MHC class II alpha or class III genes. The map we have obtained shows that the B complex does not contain well defined class I and class II regions since B-F and B-L beta genes are closely associated with unrelated genes. Moreover, class II beta genes are very closely linked to class I genes in two clusters, and to the NOR in a third one.

Amino Acid Sequence↗

PubMed1990

Studies on the bovine major histocompatibility class I and class II antigens using homozygous typing cells and antigen-specific BoT4+ blast cells.

Animals were identified from two sire lines as being homozygous for the class I bovine lymphocyte antigen (BoLA-A) w23. These animals were also shown to be homozygous for class II antigens (BoLA-D) which, however, differed between the two sire lines. Lymphocytes from these animals were then used either as stimulator cells in one-way mixed lymphocyte reactions (MLR) with all animals in the herd carrying the w23 antigen or as antigen presenting cells to bovine T4+ cell blasts. It was shown that, within each sire line, the genes encoding the MHC class I and class II antigens were closely linked. There were no detected recombinations between the MHC class I and class II regions nor within the BoLA-D region responsible for mixed lymphocyte reactivity. MLR typing of MHC class II antigens correlated with the results from T-lymphocyte proliferation studies. Cells from these cattle, which are homozygous at the class I and II MHC loci but differ in the class II antigen expressed, could be used to type the BoLA-D of other cattle.

Animals↗

PubMed1991

Production of alloantisera against class II bovine lymphocyte antigens (BoLA) by cross-immunization between class I matched cattle.

This paper describes the production of alloantisera directed against bovine major histocompatibility complex (MHC) (BoLA) class II antigens in animals whose MHC phenotypes had been defined by one dimensional isoelectric focusing. Animals of closely matched BoLA class I types were selected by serology and subsequently typed for class I and class II by 1D-IEF of immunoprecipitated antigens. Those with similar class I type by both methods, but differing at the class II locus, were chosen for reciprocal immunization. Cross-immunization was by two skin implantations 6 weeks apart. The resulting antisera showed low titre after the first immunization and elevated titre 3 weeks after the second immunization. The sera reacted strongly with cells expressing specific BoLA class II antigens. The pattern of reactivity correlated well with IEF class II typing on a panel of animals representing all of the class II IEF types present in the Friesian population.

Animals↗

PubMed1990

The biosynthetic pathway of MHC class II but not class I molecules intersects the endocytic route.

We studied the intracellular traffic and subcellular distribution of MHC class I and class II antigens in comparison with a recycling surface glycoprotein, the transferrin receptor (Tfr), in the human lymphoblastoid cell line JY. No internalization was detectable for class I molecules. Class II molecules were internalized but did not recycle. In contrast, Tfr was found to internalize and recycle. The biosynthetic pathway of class II molecules differ from that of class I molecules in that it shows a delay (1-3 hr) in transport from trans-Golgi to cell surface: here it intersects the endocytic route. Immunoelectron microscopy using anti-MHC antibodies revealed the existence of vesicular structures that were intensely labeled for class II molecules. It is proposed that at this site combination of class II molecules with processed antigen could occur.

B-Lymphocytes↗

PubMed1990

HLA class I and class II antigen expression on squamous cell carcinoma of the head and neck.

We compared human major histocompatibility (HLA) class I and class II antigen expression on squamous cell carcinoma of the head and neck with that on normal mucosa. Frozen sections of a consecutive series of 30 squamous cell carcinomas were stained with the monoclonal antibodies W6/32 (class I) and anti-DR (class II) using an immunoperoxidase technique. Normal mucosa showed class I and class II expression in the basal layers only. Class I expression on tumors was diffuse in 87%, patchy in 10%, and scattered in 3%. Class II expression on tumors was diffuse in 20%, patchy in 53%, scattered in 20%, and absent in 7%. Patterns of expression did not correlate significantly with clinical parameters, including survival, except that class II diffuse and patchy patterns were found to correlate with more poorly differentiated tumors.

Adult↗

PubMed1991

A subpopulation of mouse cytotoxic T lymphocytes recognizes allogeneic H-2 class I antigens in the context of other H-2 class I molecules.

Recently, independent lines of evidence strongly suggested that peptides derived from one foreign major histocompatibility complex (MHC) molecule bound to another MHC molecule can give rise to multiple composite MHC complexes that are able to stimulate allo-(xeno)-reactive T cells. In this study, we describe that in vivo immunization of mice with cells mismatched with the recipient for a single class I antigen results in the induction of CD8+ cytotoxic T lymphocytes (CTL) specific for allogeneic class I locus products (Dd, Kd, Dq) in the context of other class I molecules (Ks, Kd, Kk) present on stimulator cells. Evidently, the target antigen for these class I-restricted alloreactive CTL is not the native class I molecule but peptides derived from endogenous processing of allogeneic class I products presented by class I molecules. Using a combination of limiting dilution and split-well analyses, we estimated for Kk-restricted Dq-specific alloreactive CTL a precursor frequency (CTLpf) that was approximately 10 times lower than the CTLpf for "classical" nonrestricted Dq-specific alloreactive CTL. These data suggest that H-2 class I peptides presented by intact H-2 class I molecules are allostimulatory, supporting the concept that the capacity for presentation of MHC peptides by MHC molecules constitutes a part of the allogeneic immune response.

Animals↗

PubMed1985

Altered distribution of class I and class II MHC antigens during acute pancreas allograft rejection in the rat.

The expression of MHC class I and class II antigens was investigated in a model of acute pancreas allograft rejection in the rat. Pancreaticoduodenal and duct-ligated DA(RT1a)-to-LEW(RT1(1] and LEW(RT1(1]-to-LEW.1U(RT1u) pancreas grafts were compared with normal organs and with LEW(RT1(1] isografts at daily intervals from day 1 to day 10 after transplantation. The results show profound changes of MHC antigen distribution in allografts during the process of rejection. Exocrine acinar cells, being class-I-antigen-negative in the normal pancreas, strongly express these antigens during rejection. Class II antigens, normally not found in pancreatic endothelia or parenchymal cells, appear in duct epithelia, acinar cells, and endothelia of big vessels. Endocrine islet cells and smooth muscle cells stay Ia-negative throughout the rejection process. Focal class I reactivity is also observed in acinar cells of pancreaticoduodenal isografts; but class II antigens are neither seen in parenchymal cells nor in endothelia of any isograft. Thus, in the rat pancreas allograft model, the induction of class II antigens is an early phenomenon characteristic of an ongoing immune response, and it provides a valuable new diagnostic criterion. Antibodies reactive exclusively with donor-haplotype antigens demonstrate an increase in donor-derived class I and class II antigen-positive interstitial cells in addition to parenchymal antigenic changes. A possible effect of the antigenic alteration described on the course of the rejection process is discussed.

Animals↗

PubMed1986

Expression of class I and class II major histocompatibility antigens in normal and transplanted human heart.

The expression of monomorphic determinants of class I and class II histocompatibility antigens in human heart before and after cardiac transplantation was examined using monoclonal antibodies and an immunoperoxidase technique. Thirty-five biopsy specimens were examined. Seven were from nontransplanted hearts and 28 were from patients who had received orthotopic cardiac transplantation 5-270 days previously. In normal hearts no class I was found on the surface of the myocardium, but intercalated discs were occasionally stained and interstitial structures (blood vessels and discrete mononuclear cells) strongly expressed the antigen. In contrast, of the 28 specimens from transplanted patients, 24 expressed class I antigen strongly on the outer surface and intercalated discs of the myocardium as well as on the interstitial structures. Class II antigen was not found on the myocardium of normal heart. It was present on small capillaries, the endothelia of some large capillaries, and discrete mononuclear cells. In 20 of 25 samples from transplant patients there was increased expression of class II antigen on interstitial structures but not on myocardium. The increased expression of class I antigen on the myocardium following transplantation may make it a potential target for cytotoxic T cells. The relevance of increased expression of class I and class II antigens in response to transplantation is discussed.

Adolescent↗