Role of HLA antigens in Rh (D) alloimmunized pregnant women from Mumbai, Maharashtra, India.

Immunogenetic studies in various diseases provide potential genetic markers. We have studied the incidence of HLA A, B, C, DR and DQ loci antigen in Rh (D) antigen isoimmunized mothers compared to those nonimmunized isoimmunized Rh negative mothers. Seventy six mothers who were immunized to Rh (D) antigen due to pregnancy (responders) and fifty four mothers who did not develop Rh (D) isoimmunization despite positive pregnancies (nonresponders) were selected for the study. Standard methods of serological HLA typing, ABO and Rh (D) groups, and screening for Rh D antibodies were used. 392 unrelated individuals from the population were compared as controls. In addition 45 unrelated individuals from the same population were typed for HLA DRB and DQB gene using PCR-SSP kits. The genotype frequencies of HLA A2, A3, A28, B13, B17, B35, B52, B60, Cw2, Cw6, DR4, and DQ3 were significantly increased, while the frequencies of the HLA A11, A29, A31, B7, B37, B51, Cw1 and DR9 were decreased in the responder women when compared to the non-responder women. HLA A30 (19) split antigen was not identified in immunized women while HLA A23 (9) split antigen was not identified in non immunized women. HLA A3, B17, Cw2 and DR4 showed a significant relative risk among the immunized responder women. When compared with Rh immunized women (responders) reported from USA, England and Hungary the phenotype frequencies of HLA A11, A24, A28, B5, B17, B40, DR2 and DR5 were increased while HLA A23, B8, B18, and DR6 were decreased in the Indian Rh immunized women. Two locus haplotype frequency analysis observed among the responders women revealed that among the significant haplotypes expressed A2-B5, B7-Cw1, DR2-DQ1 were highly significant haplotypes in positive linkage, while A1-B5, and A1-B7 were in significant negative linkage disequilibrium. The haplotype frequencies were <or= one when these common hapoltypes were compared with control population. Thus in the present study it is evident that the inheritance of HLA A3, B17, Cw2 and DR4 increases the relative risk factor by 2.6 times among Indian Rh isoimmunized women. Further, it is evident that there are significant differences in the observed HLA antigen frequencies and two locus haplotypes in Rh isoimmunized women when compared to women from USA, UK and Hungary due to extreme HLA polymorphism in different populations of the world.

Frequency of HLA antibodies in south India.

Sera from 4088 pregnant women (649 antenatal bleeding and 3439 post-partum bleeding) living in Madurai, were collected and screened for anti-HLA. Α, Β and DR antibodies. 696 of them were screened for anti-HLA DR antibodies. Ten per cent (65/649) of antenatal sera and 13·4% of post-partum sera (463/3439) were positive for HLA A and Β antibodies: nonetheless the percentage of monospecific sera were almost the same in both. Screening for HLA DR antibodies were carried out using platelet absorption in test tray technique: seventy three of 696 (10·5%) were positive. The incidence of anti-HLA A, B antibodies correlates to the allelic frequencies in the population. Thus in India, collection and screening post-partum haemorrhage is the simplest and cost effective method of acquiring polyclonal sera for routine laboratory and diagnostic use.