HLA antigens in Asian Indians: HLA-D-DR relationships

HLA-D typing in Austria. A panel study using 26 newly defined homozygous typing cells

A panel of 120 HLA-A, -B, -C and -DR typed Austrians has been typed for HLA-D by the use of 26 Homozygous Typing Cells (HTC). The new Austrian HTC, partly defined by the 9th International Histocompatibility Workshop (9WS), partly by a checkerboard experiment with internationally well defined reference HTC, type for HLA-Dw1 to -Dw7 and an obviously new, so far unknown HLA-DR2 related HLA-D determinant. Associations of HLA-DR and HLA-D antigens in Austria and their frequencies are determined. Antigen frequencies in Austria are compared to frequencies in other Caucasoid populations.

HLA-Dw specificity assignments are independent of HLA-DQ, HLA-DR, and other class II specificities and define a biologically important segregant series which strongly activates a functionally distinct T cell subset

Several lines of evidence indicate that HLA-Dw, as defined by HTC typing, is not the result of the combined stimulatory effect of HLA-DR and DQ. Therefore, responder cells do not have to share HLA-DQ antigens with the stimulator HTCs to give a typing response. The common HLA-DR-DQ associations observed in HTCs correspond to different patterns of linkage disequilibrium in different populations. HLA-DQ and HLA-Dw are functionally heterogeneous. Although HLA-DQ molecules may play a role in primary stimulation, this role is distinct from that of Dw determinants which have strong lymphocyte activating properties. The role of the HLA-DQ determinants on the other hand, is one of modulating the total T cell response by controlling the proliferation of suppressor and cytotoxic cells. The primary MLC response is the result of the proliferative effect of HLA-Dw, DR, DP, and other associated determinants, in conjunction with a modulatory effect of DQ molecules. However, HLA-Dw (as detected by HTC typing) are DR associated determinants which are immunodominant in primary MLR. The genes of the HLA-DR subregion have been named DR by the WHO nomenclature committee. This subregion encodes the HLA-DR specificities and the DRw52 and DRw53 determinants. Unfortunately this nomenclature does not take into account the need to define the genetic basis of the HLA-Dw determinants--whether they are encoded by separate genes within the HLA-DR subregion or whether they are encoded by as yet unspecified genes in the HLA class II region in linkage disequilibrium with HLA-DR DRw52/53. There are at least three and possibly four beta chain genes in the HLA-DR subregion, all in strong linkage disequilibrium with each other. Some of these are expressed in most haplotypes while others are not; some behave as pseudogenes in some haplotypes and in others, all the genes are expressed. All the genes of the class II region have not been fully characterized. HLA-Dw determinants may be specified by one or more of these genes. When more information becomes available, the genetic and molecular basis of the HLA-Dw series as well as the functional heterogeneity and antigenic strength of the various class II determinants will be better understood.

Distribution of HLA antigens in a sample of the North Indian Hindu population

The Indian population can be divided broadly into Dravidians and the Aryans. In this report, we have attempted to analyze the HLA genetic profile of 400 native North Indian Hindus of Aryan descent. The gene frequencies of a majority of class I and II antigens show similarity to the Caucasoid population. An interesting finding was a complete lack of antigen B14 while B16 and B41 occurred with the least frequency. Haplotype A10, B8 with significant positive linkage disequilibrium as well as showing the highest incidence is characteristic of North Indians.

HLA antigens in South India: I. Major groups of Tamil Nadu

HLA-A, B profile of 385 normal healthy individuals living in Tamil Nadu, India was studied by microlymphocytotoxicity testing. Antigen, gene and haplotype frequencies of this population were calculated and compared to those already available in the literature. The sample was further divided into four major groups and the frequencies calculated. Genetic distances between the various major groups were also calculated: the analyses suggest that these different groups may differ by origin. The study further reveals that in any HLA genetic and disease association studies in India, one should give due consideration to the caste system of the sample studied.

HLA-A,B,C and DR antigens in Asaro speakers of Papua New Guinea

The HLA profile of the Asaro speakers of Papua New Guinea exhibits restricted polymorphisms. Antigens like AW24, MT1, and MB1 were present in almost every individual assayed. A CW6-related antigen and a DR locus antigen FT19 (a split of DRW6), not previously found in Pacific populations, were observed in a significant number of individuals. Ancestral HLA-B,C haplotypic combinations, such as B13, CW4 and BW60,CW3, were frequently found. Preliminary evidence is provided for an association between BW62 and CW65 in this population. The observed distributions of multiple-locus heterozygosities are similar to those expected under the null hypothesis of linkage equilibrium. The results indicate that the Asaro, among other highland populations, have been isolated long enough for pre-existing linkage disequilibria at recombinational distances of 0.8% or more (such as occur with HLA-A,B and HLA-B,DR haplotypes) to have broken down.

HLA polymorphisms in a Shanghai Chinese population

The frequencies of the HLA-A, B, C, D, DR and MB antigens have been determined in a homogeneous Shanghai Chinese population. Comparisons with the HLA-A and -B frequencies in other subsets of the Chinese population revealed some marked differences. No comparisons were possible for the D, DR and MB antigens since there were no previous studies of the antigens in those loci. We suggest that studies of the Chinese population should be confined to clearly defined homogeneous subsets. In this manner, the confounding effect of population heterogeneity may be avoided, and it is this heterogeneity which calls for extensive surveys of the huge Chinese population.

Anti-idiotypic antibodies to anti-HLA receptors induced by pregnancy

We have previously shown that lymphoblasts alloactivated in vitro acquire the capacity of stimulating the autologous mixed lymphocyte response. This response is anti-idiotypic in nature because lymphocytes so primed display accelerated memory responses only when restimulated by autologous lymphoblasts that have been alloactivated against the same HLA-DR antigen. Based on this observation we have postulated that the absence of HLA antibodies in alloimmunized human subjects may be due to the development of autoantibodies that react with the anti-HLA receptors expressed by primed lymphocytes or by anti-HLA antibodies or both. This hypothesis has been confirmed in the present investigations which show that sera from parous women react with autologous T lymphoblasts primed in 5-day mixed lymphocyte culture against their husband-i.e., with lymphoblasts expressing receptors for the immunizing donor. Anti-HLA receptors expressed by T and B lymphocytes seem to share serologic determinants because sera that bind to autologous alloactivated lymphoblasts are also capable of inhibiting the anti-HLA activity of autologous and homologous sera. Auto-anti-idiotypic antibodies inhibit the autologous mixed lymphocyte response to autologous alloactivated lymphoblasts, a phenomenon whose in vivo correlate may reside in autoinhibition of anti-HLA antibody formation and of allograft immunity. Because auto-anti-idiotypic antibodies were found in sera from all parous women tested, the hypothesis that nonresponsiveness to alloantigens exists as a state per se is not likely. The passive transfer of antireceptor (idiotype) immunity by use of antibodies from pregnant women's sera may provide a powerful tool for specific suppression of allograft rejection.