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T Lehner

Publications and source records attributed to T Lehner.

At least 109 records · Page 6Linked to original sources
PubMed1993

Two new approaches toward linkage heterogeneity of FAD: two-locus models and age of onset as a discriminator.

We present two new approaches to the problem of genetic heterogeneity encountered in linkage analysis of familial Alzheimer's disease. We used two-locus models to represent the possible existence of two disease genes while allowing for intrafamilial heterogeneity, and modeled the occurrence of the early onset form of the disease with epistasis. We developed a mixture model of heterogeneity where the early and late onset family types can be either linked to chromosome 19, 21, or unlinked, and where it is not necessary to arbitrarily preclassify a family into an early or late onset family type.

Age of Onset↗
PubMed1993

A protein fragment of streptococcal cell surface antigen I/II which prevents adhesion of Streptococcus mutans.

Attachment of Streptococcus mutans to the tooth surface involves a cell surface protein with an M(r) of 185,000, termed streptococcal antigen (SA) I/II. Four overlapping fragments of the gene encoding SA I/II were amplified by polymerase chain reaction, cloned, and expressed in Escherichia coli. The recombinant polypeptides were assayed for adhesion-binding activity to salivary receptors and for recognition by a panel of monoclonal antibodies (MAbs) raised against SA I/II. Two of the MAbs which are known to prevent colonization of S. mutans in vivo bound the recombinant polypeptide comprising residues 816 to 1161. In vitro adhesion of S. mutans to saliva-coated hydroxyapatite beads was also inhibited specifically by a polypeptide (residues 816 to 1213) encompassing the same region. The evidence from the MAbs preventing colonization of S. mutans and the adherence inhibition assay suggests that an adhesion-binding activity resides within the portion of SA I/II comprising residues 816 to 1213, which is highly conserved among oral streptococcal species.

Animals↗
PubMed1993

Mapping major and minor T-cell epitopes in vitro and their immunogenic or tolerogenic effect in vivo in non-human primates.

The immunogenicity of synthetic peptides of in vitro mapped T- and B-cell epitopes from a Streptococcus mutans cell-surface antigen were investigated in non-human primates. Peptide (1-15) contains T-cell (7-15) and B-cell (8-13) epitopes, but is only immunogenic if dimerized (1-15)2 or linked to the carrier tetanus toxoid (1-15)TT. Monomers and dimers of T- and B-cell epitopes were prepared and used to immunize macaques. Immunogenicity was assayed in lymphocytes by the uptake of [3H]thymidine and serum antibodies by a solid-phase radioimmunoassay. Macaques immunized with the dimerized (1-15)2 or carrier-linked peptide (1-15)TT exhibited in vitro T-cell proliferative responses to peptides (1-15) and (7-15). T cells from animals immunized with peptides (1-15), (7-15) or (7-15)2 failed to elicit an immune response. In order to establish if these non-immunogenic peptides might induce tolerance, the same macaques were challenged with the immunogenic peptide (1-15)TT. The results suggest that T-cell responses to peptide (1-15) were reestablished, but instead of responding to peptide (7-15) they were stimulated by a hitherto silent epitope (1-7). Tolerance to the major T-cell epitope (7-15) and the expression of a minor (silent) T-cell epitope (1-7) was associated with B-cell tolerance, suggesting that T-cell help for antibodies resides in the major T-cell epitope (7-15). However, short-term T-cell lines revealed T-cell responses to peptides (1-7) and (7-15) in both tolerized and immunized macaques, but the relative frequency of the minor epitope (1-7)-reactive lines was significantly higher in tolerized animals, whilst that for the major epitope (7-15) was higher in immunized animals. These findings suggest that the silent epitope (1-7) is really cryptic, in that it can be detected if the cell lines are first expanded in vitro with the whole peptide (1-15) and then stimulated with the truncated peptides (1-7) or (7-15). The results are consistent with the concept of a hierarchy of major and minor T-cell epitopes, now demonstrated in non-human primates, in which tolerance to the major T-cell epitope is associated with tolerance to antibody formation and the emergence of a minor T-cell epitope.

Animals↗
PubMed1992

Induction of mucosal and systemic immunity to a recombinant simian immunodeficiency viral protein.

Heterosexual transmission through the cervico-vaginal mucosa is the principal route of human immunodeficiency virus (HIV) infection in Africa and is increasing in the United States and Europe. Vaginal immunization with simian immunodeficiency virus (SIV) had not yet been studied in nonhuman primates. Immune responses in macaques were investigated by stimulation of the genital and gut-associated lymphoid tissue with a recombinant, particulate SIV antigen. Vaginal, followed by oral, administration of the vaccine elicited three types of immunity: (i) gag protein p27-specific, secretory immunoglobulin A (IgA) and immunoglobulin G (IgG) in the vaginal fluid, (ii) specific CD4+ T cell proliferation and helper function in B cell p27-specific IgA synthesis in the genital lymph nodes, and (iii) specific serum IgA and IgG, with CD4+ T cell proliferative and helper functions in the circulating blood.

Administration, Oral↗
PubMed1992

A mechanism of passive immunization with monoclonal antibodies to a 185,000 M(r) streptococcal antigen.

The cell surface streptococcal antigen (SA) I/II of 185,000 M(r) is an immunodominant molecule that expresses one or more adhesion determinants. A series of 14 monoclonal antibodies (MAb) to defined parts of SA I/II were generated and some of these were used in passive immunization of macaques. Topical administration of selected MAb to the teeth of macaques prevented colonization of endogenous or implanted exogenous Streptococcus mutans for a period of 1 year. Significant reduction of both smooth surface and fissure caries was found in macaques who had MAb (Guy's 1) applied to their teeth, as compared with saline-treated animals. A series of in vivo passive immunization experiments was then carried out in 57 human subjects. Topical application of MAb to SA I/II prevented colonization of both artificially implanted exogenous strains of S. mutans, as well as natural recolonization by indigenous S. mutans. The properties of the protective MAb were then investigated and the epitope specificity within the SA I/II molecule was found to be essential but not the isotype specificity of the immunoglobulin (Ig). The requirement for complement activating and the phagocyte binding sites of the Fc fragment of MAb was not essential, as the F(ab')2 fragment of the MAb was as protective as the intact IgG, but the Fab fragment failed to prevent recolonization of S. mutans. Prevention of recolonization was specifically restricted to S. mutans, as the proportion of other organisms, such as S. sanguis, failed to show a significant change. The surprising feature of these experiments was that protection of re-colonization of S. mutans lasted up to 2 years, although MAb was applied for only 3 weeks and functional MAb was detected on the teeth only 3 days following application of the MAb. The long-term protection could therefore not be accounted for by a persistence of MAb on the teeth, but may be due to a shift in the microbial balance in which other bacteria occupy the ecological niche vacated by S. mutans, resulting in colonization resistance to S. mutans. Gene cloning and sequencing the SA from S. mutans, S. sobrinus and S. sanguis identified a conserved region (residues 955-1213) which on Southern hybridization and partial DNA sequence analysis was also found in 19 alpha-haemolytic oral streptococci. The results suggest that the SA molecule may constitute a family of adhesins in oral alpha haemolytic streptococci.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Linkage analysis of spinal muscular atrophy.

Linkage data between four markers on chromosome 5 confirm and extend our previous studies that localized the mutation in spinal muscular atrophy to 5q11.2-q13.3. Localization of D5S6 by in situ hybridization refines the mapping of the defective gene to the region 5q12.2-q13. We also report the use of a highly informative PCR-based polymorphism with five alleles. This RFLP will be particularly useful for prenatal diagnosis where only old tissue samples from affected individuals are available. The high heterozygosity of this locus should also assist in identifying recombinants that will refine the genetic mapping of the mutation.

Chromosome Mapping↗
PubMed1992

T and B cell responses following immunization with tetanus toxoid in IgA nephropathy.

The B and T cell responses were investigated in IgA nephropathy before and after immunization with tetanus toxoid (TT). Both IgA and IgG anti-tetanus toxoid antibodies were elicited, but the IgA antibodies were significantly greater in patients (92.6 +/- 11.7 ELISA units) than in the controls (49.2 +/- 7.5 ELISA units). This was associated with a significantly greater proportion of IgA+ B cells in patients than controls before immunization. However, a significant increase in the proportion of IgA1 binding CD4 and CD8 cells was also found. The proportion of CD3 cells with gamma delta T cell receptors (CD3+TCR gamma delta +), was significantly greater before immunization in the IgA nephropathy patients (37.0% +/- 2.4), compared with controls (10.0% +/- 2.3; P less than 0.001). Immunization with TT further enhanced the CD3+TCR gamma delta + cells in patients to 45.8% +/- 7.2 compared with controls (16.3% +/- 4.5), with a corresponding decrease in CD3+TCR alpha beta + cells in the patients (P less than 0.001). CD3+TCR gamma delta + cells are upregulated by common microbial antigens and clinical exacerbations of IgA nephropathy are frequently associated with mucosal infections and a rise in serum IgA concentration. The increased TCR gamma delta expression may be responsible for the enhanced IgA antibody response in IgA nephropathy. The increase in IgA antibodies may than exert a controlling effect by binding to augmenting T cells and thereby inhibiting their function.

Adult↗
PubMed1992

Expression and gene transcript of Fc receptors for IgG, HLA class II antigens and Langerhans cells in human cervico-vaginal epithelium.

The mechanism of transmission of HIV from the male to the female genital tract or in the reverse order is not clear. CD4 glycoprotein is the receptor for HIV and Langerhans cells and the related dendritic cells could play a role in the initial transmission of HIV. Fc receptors (FcR) for IgG might be involved in antibody-mediated binding of HIV. We carried out an immunohistological study of normal human cervical and vaginal epithelia for the presence of CD4 glycoprotein, Langerhans cells and FcR to IgG. CD4+ glycoprotein was not found in the vaginal or cervical epithelium, with the exception of a few endocervical epithelial cells. A small number of CD4+ mononuclear cells were found in the endocervical epithelium of a third of the specimens but a large number of CD4+ cells was found in the submucosa of most of the cervical and vaginal specimens. Langerhans cells expressing CD4, HLA class II, Fc gamma R2 and Fc gamma R3 were detected in most vaginal, ectocervical and transformation zone epithelia and in 9/14 endocervical tissues. Fc gamma R3 was detected in about two-thirds of the columnar endocervical epithelium and the transformation zone. A smaller number of specimens expressed Fc gamma R2 in these epithelia, but Fc gamma R1 was not detected. We then demonstrated mRNA for Fc gamma R3 in the columnar endocervical epithelial cells and transformation zone by in situ hybridization, using a CD16-RNA probe. Fc gamma R3 and Fc gamma R2 gene transcripts were also found in fetal cervical tissue by applying the polymerase chain reaction to amplify portions of the Fc gamma R3 and Fc gamma R2 coding sequences in cDNA prepared from fetal RNA. HLA-DR was found in the endocervical cells, transformation zone and in Langerhans cells of all specimens. The presence of Langerhans cells, Fc gamma receptors and HLA class II antigen offers three potential mechanisms for cervico-vaginal HIV transmission: (i) direct HIV infection of Langerhans cells, (ii) binding of HIV antibody complexes to cervical epithelial Fc gamma receptors and (iii) binding of HIV infected CD4+ cells to cervical HLA class II antigen which may infect these or the adjacent CD4+ cells.

Adult↗
PubMed1991

Characterization of streptococcal antigen-specific CD8+, MHC class I-restricted, T cell clones that down-regulate in vitro antibody synthesis.

T cell clones were generated from the peripheral blood of rhesus monkeys that had been immunized with a soluble Mr 185,000 Ag (SAI/II) derived from Streptococcus mutans. The clones were CD3+ CD8+ CD4- alpha beta TCR+ and were specifically stimulated to proliferate by SAI/II. The proliferative responses of the cloned cells were class I restricted, as demonstrated by reconstitution of the cloned T cells with APC matched at various MHC class I and II loci, as well as by inhibition with anti-class I and not anti-class II mAb. The function of the CD8+ cloned cells was examined in vitro for their effect on antibody synthesis by Ag-stimulated CD4+ cells and B cells from immunized animals. Indeed, four of the five clones suppressed SAI/II-specific IgG antibody synthesis when activated with SAI/II and the appropriate MHC-matched APC. Although activation of the suppressor clones was Ag specific, the effector function of the suppression of antibody synthesis was Ag nonspecific. The latter was probably mediated by lymphokines and, indeed, the culture supernatant generated by stimulating the cloned CD8+ cells with anti-CD3 mAb suppressed both the specific and nonspecific antibody synthesis. Cytotoxicity studies showed that all five CD8+ clones showed a low level of lectin-dependent cytotoxicity. However, because four of the five clones expressed significant suppression of antibody synthesis, the suppressor activity was unlikely to be a function of the weak cytotoxicity. The results suggest that immunization of rhesus monkeys with a soluble streptococcal Ag induced CD8+ alpha beta TCR+ T cell clones that show SAI/II-specific, MHC class I-restricted proliferative responses and nonspecific down-regulatory function of in vitro antibody synthesis.

Animals↗
PubMed1991

An analysis of synthetic peptide restriction by HLA-DR alleles in T cells from human subjects, naturally sensitized by Streptococcus mutans.

T cells from most human subjects show significant in vitro proliferative responses to a 185-kDa surface Ag from Streptococcus mutans as well as to synthetic peptides derived from the sequence of a Mr 3800 streptococcal Ag. T cells from subjects expressing each of the alleles from DR1 to DR7 responded to synthetic peptides of 17 or 21 amino acid residues. Furthermore, inhibition studies with mAb to HLA class I and class II Ag showed that the DR Ag was a restriction molecule for the proliferative responses. Mouse L cells transfected with DR1, DR2, DR4, DR5, and DR7 were used to confirm the permissive nature of the responses. An analysis of the fine specificity of the responses showed that the minimum peptides capable of stimulating T cells from subjects with different DR types varied by one or two residues. For DR2 and DR3 the shortest peptide was residues 6-15, an additional serine (residue 5) was required for DR1 and DR7 and an aspartic acid (residue 4) for DR4, DR5, and DR6. Successful oral-mucosal bacterial colonisation in humans, by a largely commensal Streptococcus, might be associated with the permissive nature of the HLA-DR restriction of the response to a major streptococcal cell surface peptide. The peptide recognised in association with the HLA-DR molecule may induce an immune response that prevents central entry of the organism from the peripheral mucosal site.

Alleles↗
PubMed1991

The comparative frequency of human T cells responding to a native antigen and a synthetic peptide derived from Streptococcus mutans.

The frequency of human peripheral blood T cells responding to a 21-residue synthetic peptide (SP 21) derived from the sequence of a 3.8-kDa streptococcal antigen was estimated by limiting dilution analysis and compared with the frequency of cells responding to the native, cross-reactive 185-kDa streptococcal antigen. Frequency estimates were made by measuring both [3H]thymidine incorporation and IL 2 production in the same cell cultures. The results provided frequency estimates for SP 21-reactive cells of between 1:42 147 and 1:306 110, with a mean of 1:160 617 by [3H]thymidine incorporation, and 1:139 893 to 1:241 315 (mean 1:165 315) using the IL 2 assay. With the native 185-kDa streptococcal antigen, frequency estimates were between 1:38 393 and 1:86 142 (mean 1:169 934) according to the proliferative response and 1:22 462 and 1:100 400 (mean 1:61 189) by the IL 2 assay.

Amino Acid Sequence↗
PubMed1991

Localization of the gene for the Wiskott-Aldrich syndrome between two flanking markers, TIMP and DXS255, on Xp11.22-Xp11.3.

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive genetic disease in which the basic molecular defect is unknown. We previously located the WAS gene between two DNA markers, DXS7 (Xp11.3) and DXS14 (Xp11), and mapped it to the proximal short arm of the human X chromosome (Kwan et al., 1988, Genomics 3:39-43). In this study, further mapping was performed on 17 WAS families with two additional RFLP markers, TIMP and DXS255. Our data suggest that DXS255 is closer to the WAS locus than any other markers that have been previously described, with a multipoint maximum lod score of Z = 8.59 at 1.2 cM distal to DXS255 and thus further refine the position of the WAS gene on the short arm of the X chromosome. Possible locations for the WAS gene are entirely confined between TIMP (Xp11.3) and DXS255 (Xp11.22). Use of these markers thus represents a major improvement in genetic prediction in WAS families.

Chromosome Mapping↗
PubMed1991

The expression of Fc receptors for immunoglobulin G in human rectal epithelium.

The rectal mucosa is one of the routes of transmission of the HIV virus, although the mechanism of transmission is unknown. We carried out an immunohistological investigation of human rectal epithelium to detect CD4 glycoprotein and Fc receptors (FcR) for immunoglobulin G which may be involved in HIV infection. CD4 was not detected by monoclonal antibodies (MAb) in normal rectal epithelial cells, although CD4+ mononuclear cells were found in the lamina propria of the rectum. FcR3 and FcR2 were, however, detected in surface or crypt epithelial cells of rectal mucosa, using MAb to CD16 and CD32, respectively. In addition, CD16 messenger RNA (mRNA) was found in surface and crypt epithelial cells by in situ hybridization using an RNA probe. FcR3 and FcR2 were also detected in fetal recto-colonic tissue by immunohistology, suggesting that these are constitutive receptors. FcR3 and FcR2 gene transcripts were then demonstrated in fetal recto-colonic tissue using the polymerase chain reaction to amplify a portion of FcR3 and FcR2 coding sequences in complementary DNA (cDNA) prepared from fetal RNA. These findings suggest the possibility that rectal transmission of HIV-antibody complexes might be facilitated by the expression of FcR3 and FcR2 in rectal epithelial cells.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Detection of HSV-1 DNA in patients with Behçet's syndrome and in patients with recurrent oral ulcers by the polymerase chain reaction.

The polymerase chain reaction was used to detect HSV-1 DNA in genomic DNA extracted from peripheral blood leucocytes, in patients with Behçet's syndrome (BS), patients with recurrent oral ulcers and normal healthy controls. A 211-bp HSV-1 DNA fragment was found in a significant number of patients with BS (p less than 0.02). Serum anti-HSV-1 antibodies were also found in a higher proportion of patients with BS (p less than 0.02) than in healthy controls. However, virus-specific DNA was not detected in biopsy samples taken from oral ulcers in patients with BS.

Antibodies, Bacterial↗