Analysis of Pregnancy-Induced Anti-HLA Antibodies Using Luminex Platform

The impact of pregnancy on the incidence of HLA sensitization is poorly explored, and most of the data were obtained by use of a complement-dependent cytotoxicity (CDC) assay with an incidence of 18% to 30%. In many cases, antibodies cannot be detected by CDC as their level fades in time. However, this state of "latent" sensitization can still have a significant clinical impact in a subsequent transplantation setting.

Pregnancy-induced HLA sensitization was analyzed in 69 mothers without a history of transfusions or transplants. The mothers and their offspring were typed for HLA-A, HLA-B, and HLA-DR. Sera from the mothers were studied using the Luminex screening test to detect anti-HLA class I and class II antibodies. Positive and borderline sera were further analyzed using single antigen kits.

Thirty-four sera (49.3%) were positive in the screening test (52.9% for class I and 61.7% for class II antibodies). All of them tested positive for paternal alloantigens by single antigen. Positive paternal alloantigens were also detected in 52.9% of class I and 36.3% of class II sera with borderline screening. Interestingly, in a further analysis, the mean of the MFIs of paternal alloantigens that resulted negative was calculated and compared with that of neutral alloantigens and that of maternal self-antigens; in both cases, differences were highly significant (288 vs 153, P < .0001; 288 vs 102, P < .0001; respectively).

This study shows a high incidence of pregnancy-induced HLA sensitization and suggests that HLA typing of partners of women who have been pregnant may contribute to a better risk assessment in the transplantation setting.