Experimental and clinical immunogenetics最新文献

The HLA-B41 specificity was first identified over 25 years ago and, although both serological and biochemical studies have suggested its subdivision, it is only recently that two HLA-B*41 alleles (B*4101 and B*4102) have been identified and sequenced. We designed three oligonucleotide primers, combined in two mixtures to define these alleles by PCR using sequence-specific primers (PCR-SSP) in a random normal population of 9,464 HLA-A, B, DR, DQ typed Northern European Caucasoid donors from the Welsh Bone Marrow Donor Registry. The HLA-B41 phenotype frequency was 0.835%, and of the 79 HLA-B41 subjects 22 (27.85%) were B*4101 and 57 (72.15%) were B*4102. The phenotype frequencies of B*4101 and B*4102 were 0.232 and 0.602%, respectively, and the gene frequencies were 0.00116 and 0.00301, respectively. Formal two-locus linkage disequilibrium (LD) analysis demonstrated significant associations between B*4101 and A30 and DR11, and between B*4102 and A66 and DR13. LD analysis of three loci showed significant associations between B*4101, DR7, DQ2 and B*4101, DR11, DQ7 (DQB1*0301/0304) and between HLA-A3, B*4102, DR13; A66, B*4102, DR7; A66, B*4102, DR13; B*4102, DR13, DQ6 and B*4102, DR13, DQ7. Examination of the HLA phenotypes (including HLA-C) of the B*41 subjects, together with the LD analysis findings, suggested four different HLA haplotypes bearing B*4101 and five B*4102 haplotypes. The most frequent B*4101 haplotype was: HLA- A30 or other A allele, Cw*1701, B*4101, DRB1*1102, DQB1*0301 and the most freqent B*4102 haplotype was: A*6601 or A3 or other A allele, Cw*1701, B*4102, DRB1*1303, DQB1*0301. In addition, the well-known association of A66 with B41 was between A*6601 and B*4102, and although both B*41 alleles were commonly in association with Cw*1701, B*4101 was found with Cw*07. One-dimensional isoelectric focusing (1D-IEF) analysis of HLA-B proteins from 2 B*4101 and 2 B*4102 subjects clearly showed that the B41.1 and B41.2 1D-IEF variants, identified in the 10th International Histocompatibility Workshop, corresponded to B*4101 and B*4102 products, respectively. Serological titration studies, with 59 lymphocytotoxic pregnancy antisera, containing an HLA-B41 component and stimulated by up to five different HLA-B specificities, were unable to differentiate the two groups of B*41 subjects. This suggests that partition of the HLA-B41 specificity will not normally be achieved by classical serological methods. It is suggested that the previous alleged serological subdivision of HLA-B41 was founded on the unwitting use of antisera detecting the HLA-Cw*17 products.

The HLA-DMA gene, along with the HLA-DMB gene, encodes the not classical class II molecule. This molecule catalyzes the class-II-associated invariant-chain peptide (CLIP)-antigen peptide exchange in classical class II molecule peptide-binding groove. As such, the DM heterodimer is an antigen presentation regulator and may be linked to immune system deficiencies such as those observed in autoimmune diseases. The study of DMA gene polymorphism seems be a reasonable approach to provide an answer to this question. Thanks to PCR-derived methods, the relationship between DMA gene polymorphism and rheumatoid arthritis (RA) was demonstrated in the present study. The DMA*0101 allele was observed to confer a significant predisposition to RA while the DMA*0102 allele significantly protected from this disease. Polymorphism experiments with the HLA-DRB1 gene revealed that this relationship between DMA polymorphism and RA is not a consequence of a linkage disequilibrium with the HLA-DRB1 alleles implicated in this pathology. The study of the DMA gene could therefore prove to be very useful in the early diagnosis of RA.

A high percentage of human fetal and postnatal thymocytes express MHC class II molecules. This raises the possibility that human thymocytes in early life are able to present peptides to other immature T cells and thereby initiate thymic selection of these cells. Here we address this question by exposing newly harvested infant thymocytes to superantigen (Sag) which binds to the T-cell receptor and to MHC class II chains outside the peptide binding groove. The results show that the thymocytes are able to present Sag and to be activated to proliferation as well as apoptosis by Sag presented by other thymocytes. The absence of responses to Sag with mutations in class II binding sites showed that class II molecules were necessary for the responses, and very low expression of class II molecules on CD4-8- cells indicates that the demonstrated T-cell/T-cell interactions are confined to T-cell receptor-positive CD4+8+, CD4+8-, and CD4-8+ cells. These latter subsets were shown to be able to present Sag to each other. These findings suggest that class II+ thymocytes may participate in the selection of self-restricted T cells during a critical period in the shaping of the human immune system.

Immunoglobulin (Ig) allotypes are polymorphic genetic systems that show distinct racial arrays, thus making them powerful tools for studies of genetic admixture and biological relationships. In the province of Sorsogon, southern Luzon, Philippines, allotyping was completed on 252 persons residing in two neighboring villages. The people demonstrated 14 GM and 3 KM phenotypes. The frequency of homozygous KM3, KM1 and heterozygous KM1,3 was identical in these villages; however, half of the GM phenotypes present in one village were significantly less frequent in the other village. The frequency of KM and GM haplotypes was different from those reported in Filipino aboriginal groups, but similar to a population on Samar Island, the only other Filipino group for which Ig allotype data exist. Variability in the prevalence of parasitic disease such as lymphatic filariasis may in part reflect differences in genetic susceptibility, resulting from allotypic heterogeneity between villages.

Five new polymorphisms in the C7 gene are described: 2 in intron 1, and 1 each in introns 7, 8 and 15. Four of these are single nucleotide exchanges, while the fifth is a T insertion at 10 sequential Ts. Allele frequency data are presented for intervening sequence (IVS)1+ 55 in 6 normal population groups. We present new and updated data in these populations on a previously described C7 polymorphism in exon 13 (cDNA 1792 A/T). We also report the extended haplotypes associated with C7 deficiency for which marker investigation is a useful, and in some cases vital, adjunct to the identification of the gene defects. Almost without exception, a particular haplotype is associated with a particular mutation causing the deficiency state. Haplotyping is especially useful where polymerase chain reaction failure on one chromosome could be a cause for difficulties in detecting a molecular defect due to heterozygosity for large deletions or unidentified variations at the locations of the primers.

Ligation of the major histocompatibility complex class I molecules (MHC-I) on human T lymphoma cells (Jurkat) initiates p56(lck)-dependent intracellular signalling events (phosphotyrosine kinase activity; [Ca(2+)](i)) and leads to augmented growth inhibition and apoptosis. MHC-I ligation in concert with ligation of CD2 or CD28 augments, changes or modifies the pattern of activation. Ligation of MHC-I and CD2 alone resulted in growth inhibition, whereas CD28 ligation alone had no effect on cell proliferation. Ligation of MHC-I together with CD2 augmented growth inhibition and enhanced the level of apoptosis. In parallel experiments with the p56(lck)-negative Jurkat mutant cell, JCaM1.6, cross-linking neither influenced cell signalling nor cellular growth functions, indicating a cardinal role of the src kinases in signal transduction via MHC-I, CD2 and CD28 molecules. The results presented here provide evidence for the involvement of MHC-I molecules in the modulation of signal transduction via the CD2 and CD28 costimulatory molecules.

Trichomonas vaginalis is a flagellated protozoan which causes trichomoniasis, a sexually transmitted disease of the human genitourinary tract. The importance of the alternative complement pathway in host defence against T. vaginalis was investigated in vitro. Kinetic studies utilising immunofixation following electrophoresis showed that both a strongly and weakly virulent strain of T. vaginalis activated murine serum C3. In vivo studies with congenic-resistant, C5-deficient, B10.D2/OSn- and C5-sufficient, B10.D2/nSn mice showed that the presence of C5 is a significant factor in the innate host resistance to primary infection with a strongly virulent, but not a weakly virulent trichomonad strain.

PCR-SSP was used to HLA-type a cohort of Ugandan HIV-positive individuals. The results represent a more comprehensive description of HLA in an African population than previously described and are in concordance with data from a general Black population. Substantial differences exist between this population and Caucasoid populations in which immunological responses to HIV have been investigated; this emphasises that the main HLA-restrictive elements for HIV-specific cytotoxic T lymphocytes will most likely be different for each population.