PubMed · 7169192
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E Gazit. 1982-11-01. [HLA systems--present and future].. https://pubmed.ncbi.nlm.nih.gov/7169192/
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As successful organ or marrow transplantation correlates with the degree of HLA-compatibility between patient and donor, registries have been developed to facilitate matching. However, racial minority groups have a lower chance of finding a match. We evaluate the impact of the biology of racial genetic polymorphism upon the probability of finding an HLA match for patients of different racial groups. The National Marrow Donor Program has compiled the HLA types of 20,449 patients and 1,625,159 potential volunteer donors. These HLA types were used to estimate the probability of finding an HLA-matched donor for patients of different racial groups. We estimated the HLA haplotype frequencies for different races, and then determined the probability of finding matched donors, given several hypothetical registry sizes. We confirmed that patients of minority races searching the current National Marrow Donor Program registry have low probabilities of finding matches. This was only partly due to the smaller number of donors from these racial minorities, as the observation persisted even when hypothetical donor registry sizes were the same for all racial groups. We demonstrate that African-Americans are more polymorphic with respect to HLA, and are hence less likely to find donors at any given registry size. An increase in the recruitment of minority racial groups for organ and marrow donors will only partially alleviate the problem of equal access to HLA matches for patients belonging to racial minority groups. It will therefore be important to attempt to improve methods for transplantation using HLA-mismatched donors.
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Recent studies have shown that NK cells recognize HLA-class I molecules. Moreover, the analysis of NK cell clones has provided evidence that they are capable of discriminating between different groups of HLA alleles. HLA class I recognition generates a negative signal which inhibits the NK cell cytotoxicity, thus resulting in target cell protection. HLA-class I recognition is mediated by clonally distributed receptors, some of which have been identified, characterized and cloned. The first two identified receptors were shown to be specific for HLA-C alleles, each recognizing a group of alleles sharing two amino acidic positions (77 and 80) in the peptide binding groove. The HLA-C specific receptors are represented by two 58 Kd (p58) molecules that are highly homologous, as shown by both biochemical analysis and by the comparison of the corresponding genes. Two additional receptors have been recently identified, which recognize two distinct groups of HLA-B alleles. These receptors are represented by the CD94 and by the NKB1 molecules, recognizing the Bw6 and Bw4 supertypic specificities. Recent analysis of the surface receptors involved in NK cell triggering has provided evidence that class I specific NK receptors can, in some instances, induce NK cell triggering, thus contributing to the activatory pathway of NK cells.