Alloantigen processing and presentation.
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Interest in the complexity of the HLA system and its relevance in the selection of unrelated bone marrow donors has had an important impact on our understanding of the immunogenetics of HLA and non-HLA or minor histocompatibility systems. More than 50 genes on the short arm of chromosome 6, which carries the information for HLA, have been identified and there are more to come. HLA-class I and HLA-class II each have more than 200 alleles, and the number is growing. The HLA-C antigens appear to act as targets for natural killer cells. New inroads have been made in the recognition of the minor histocompatibility antigens HA-1 to -5, which can be recognized by cytotoxic T-cell clones and are inherited in a Mendelian fashion. A mismatch for HA-1 might lead to graft-versus-host disease. The introduction of new technologies, especially polymerase chain reaction, has been immensely helpful in mapping the genetic complexity of HLA. Methodology now allows typing for HLA on the level of DNA in a matter of a few hours and is most useful when selecting a suitable bone marrow donor. The new genetic information available makes it clear that many so-called HLA matched unrelated bone marrow transplants performed in the past were actually mismatched. Nevertheless, many of them had a good clinical outcome. It is clear that one of the most important challenges is to determine which mismatched transplants will fare well and which should be avoided. Recent findings in organ transplantation might be helpful here.
Tissue typing employing the lymphocytotoxicity micro-assay was performed by introducing in the system approximately 15% of autologous or homologous ultra-centrifuged blood serum, both of peripheral and bone marrow source. As a rule, the pattern of reactivity was unaffected by peripheral blood serum, whereas the cytotoxicity was nearly always inhibited by autologous bone marrow blood serum or by homologous one from donors sharing the inhibited HL-A specificities with the donors of lymphocytes. These results suggest that at least in these patients HL-A antigens are present in bone marrow blood serum at a concentration which is definitely higher than in peripheral blood.
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The immunogenicity of single, private H-2 specificities has been tested. In most cases, the specificity was known to be confined either to H-2K or to H-2D. This was accomplished by the appropriate choice, as donor and recipient, or parent of the F(1) hybrid recipient, of congenic strains differing at H-2 only, and of recombinant haplotypes in donor and/or recipient. By nearly all tests, the H-2K antigen appeared to be a stronger immunogen than the H-2D antigen. Skin grafts with an H-2K difference showed median survival times (MST) of 9.3-14.5 days; for H-2D the values were 13.8-18.6. The difference was also present, though narrowed, for second-set grafts. H-2K grafts regularly engendered a demonstrable cytotoxic antibody response; with H-2D differences the response was absent or very weak. K end cytotoxic titers after multiple immunizations with lymphoid tissues ranged from 1/32 to 1/2,048, D end titers from 0 to 1/128. Hemagglutination titers showed no clear difference. The results of passive enhancement of skin grafts with H-2 alloantibody produced in donor recipient combinations, identical to those used for the skin grafts showed a different pattern. H-2K, despite its greater immunogenic strength was more easily enhanced than H-2D. Prolongation of MST's for H-2K was 2.4-6.7 days, for H-2D grafts, 0.2-1.5 days.
Repeated exposure to human immunodeficiency virus (HIV) does not always result in seroconversion. Understanding the conditions that permit or protect against progressive infection with HIV is important for vaccine development. Nineteen subjects at risk for HIV infection were CCR-5 genotyped and screened for virus-specific memory cytotoxic T lymphocytes (CTL). None had the Delta32CCR-5/Delta32CCR-5 genotype associated with HIV resistance. HIV-specific CTL were detected in 7 (41.1%) of 17 exposed uninfected subjects versus 0 of 14 seronegative subjects with no HIV risk factors (P=.006, chi2 test). Recognition of virus by CTL in exposed uninfected subjects was major histocompatibility complex class I-restricted and multispecific, and specificity could change with time. Activity could persist up to 34 months after the last virus exposure. The presence of HIV-specific CTL in a greater proportion of seronegative HIV-exposed versus unexposed subjects supports the notion that in some cases, virus exposure induces HIV immunity without seroconversion or disease progression.
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The association of A3, B7, Dw2 and DR2 histocompatibility (HLA) markers with multiple sclerosis (MS) is well established among Northern Europeans and Caucasoids in the United States. We showed previously that A3 and B7 were not increased among Israelis with MS, and in a preliminary study Dw2 as well. An association of A3 and B7 is also lacking in Italians, Jordanian and Japanese MS patients. In Black American MS patients, the B7 frequency is slightly increased but Dw2 is still significantly associated with MS. For the HLA-DR antigen series DR2 is shown to have a stronger association to MS than A3 and B7. Conceivably, this antigen could be associated with MS even in populations where an association with A3 or B7 is lacking. Therefore, a study of HLA-A, B, C, DR and D antigens was carried out in Israel. No significant excess or deficiency of HLA antigens was found in MS. Possible explanations for these results are as follows: (1) the relevant HLA-D alleles in the Jewish population were not detected by the homozygous typing cells (HTCs) used, since they were derived primarily from European sources; (2) in contrast to the Caucasoid populations the genetic factor predisposing for MS is not associated with HLA alleles in the Israeli population; (3) MS is an heterogeneous disease and in Israelis, an environmental factor is sufficient to cause the disease.
OBJECTIVE: To determine whether HLA and autoimmunity contribute to the pathogenesis of Blau syndrome (familial granulomatous arthritis, uveitis, and rash) and evaluate whether this condition is related to sarcoidosis. DESIGN: Large family survey. SETTING: General community, Green Bay, Wis, and two tertiary care medical centers in Philadelphia, Pa. PARTICIPANTS: Thirty-six family members and spouses from a large kindred with Blau syndrome. SELECTION PROCEDURES: Volunteer and convenience sample. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Ten affected and many unaffected subjects were personally examined. Medical records and previous biopsy reports and specimens, when available, were reviewed. Two affected subjects had skin biopsies performed and three affected adult subjects were tested with Kveim skin-test reagent. Serologic and genomic class I and class II HLA typing was performed on 27 affected and unaffected subjects. All 13 living affected subjects and the one obligate carrier had the following assays performed; antinuclear antibody titer, rheumatoid factor, serum angiotensin converting enzyme level, quantitative immunoglobulins of the IgG, IgM, and IgA classes, and clinical chemistry profiles. Several had complete blood cell counts and erythrocyte sedimentation rates performed. Four affected subjects, one possibly affected subject, and one obligate carrier were newly identified. Flexion contractures of the fingers and toes (camptodactyly) were found, for the first time, to be a phenotype characteristic. Earlier onset and worsening of symptoms in succeeding generations (anticipation) were observed. Sixteen HLA haplotypes were identified. No conclusive evidence for linkage between these haplotypes and phenotype expression could be demonstrated. All 13 affected subjects, however, carried the DR2 (DR beta 1*1501) and/or DR4 (DR beta 1*0401) allele. There was no evidence of hypercalcemia, hypergammaglobulinemia M, rheumatoid factor production, or abnormal blood cell counts. Two affected subjects had low-titer antinuclear antibody screening tests, five had mild to moderately elevated IgG and/or IgA levels, two had raised serum angiotensin converting enzyme levels, and three had mild elevation of the erythrocyte sedimentation rate. All three subjects tested with Kveim skin-test reagent showed no reactivity by visual inspection. Both subjects who had had skin biopsies performed had evidence of granulomatous inflammation. CONCLUSIONS: This family's illness is distinct from both classic and early-onset sarcoidosis. There is minimal evidence for autoimmunity and systemic inflammation. Camptodactyly should be added to the list of syndrome-defining characteristics. Although HLA haplotypes do not appear to segregate with affected subjects, HLA-DR2 and HLA-DR4 subtypes may play a permissive role in phenotype expression. This family represents a unique opportunity to define the molecular mechanisms involved in the initiation of arthritis and uveitis in humans. Genetic linkage studies to determine the chromosomal location of the Blau syndrome gene are in progress.
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The MFG test is a family-based association test that detects genetic effects contributing to disease in offspring, including offspring allelic effects, maternal allelic effects and MFG incompatibility effects. Like many other family-based association tests, it assumes that the offspring survival and the offspring-parent genotypes are conditionally independent provided the offspring is affected. However, when the putative disease-increasing locus can affect another competing phenotype, for example, offspring viability, the conditional independence assumption fails and these tests could lead to incorrect conclusions regarding the role of the gene in disease. We propose the v-MFG test to adjust for the genetic effects on one phenotype, e.g., viability, when testing the effects of that locus on another phenotype, e.g., disease. Using genotype data from nuclear families containing parents and at least one affected offspring, the v-MFG test models the distribution of family genotypes conditional on offspring phenotypes. It simultaneously estimates genetic effects on two phenotypes, viability and disease. Simulations show that the v-MFG test produces accurate genetic effect estimates on disease as well as on viability under several different scenarios. It generates accurate type-I error rates and provides adequate power with moderate sample sizes to detect genetic effects on disease risk when viability is reduced. We demonstrate the v-MFG test with HLA-DRB1 data from study participants with rheumatoid arthritis (RA) and their parents, we show that the v-MFG test successfully detects an MFG incompatibility effect on RA while simultaneously adjusting for a possible viability loss.