Kinetics of the pregnancy-induced humoral and cellular immune response against the paternal HLA class I antigens of the child.

Pregnancy can prime the maternal humoral immune response against paternal human leukocyte antigens (HLA) of the child. Previous studies have reported that formation of antibodies against inherited paternal HLA is associated with the presence of primed cytotoxic T lymphocytes (CTLs) specific for these antigens. Recently, we reported that primed CTLs can persist for more than 10 years after pregnancy even if the antibodies have disappeared. In the present study we studied the kinetics of the pregnancy induced immune response of the T-cell and B-cell compartment. In 12 women, who had specific antibodies against the paternal HLA antigens of the child (child mismatch) at the time of delivery, we analyzed the CTLp frequencies against the paternal HLA antigens from the time of delivery up to 2 years after. The contribution of primed CTLs to these CTLp frequencies was tested by limiting dilution analysis in the absence and presence of monoclonal antibodies specific for CD8. In contrast to naïve CTLs, primed CTLs are resistant to CD8 antibodies. Disappearance of the antibodies was not associated with a decrease of the number of CTLp directed against the paternal antigens, towards which the antibodies were originally directed. However, in women where the antibodies disappeared, a decrease of primed child mismatch specific CTLs was found, whereas in women where the antibodies persist, the population of primed CTLs remained stable up to 2 years after delivery. Our data suggest a functional correlation between the T-cell and B-cell allorepertoire. Although the kinetics do not run completely in parallel, disappearance of the anti-HLA antibodies in the first 2 years after delivery is related with a decrease of primed child mismatch specific CTLs. These data may be relevant for transplantation of female recipients with historical, pregnancy-induced HLA alloantibodies.