Pregnancy can induce long-persisting primed CTLs specific for inherited paternal HLA antigens

Previous studies showed that pregnancy can prime the maternal cellular immune response directed against paternal HLA antigens. Primed CTLs specific for inherited paternal HLA antigens (IPA) were found in women who had formed HLA allo antibodies, whereas naive CTLs were present in women who did not form antibodies against the paternal HLA antigens. As HLA allo antibodies may disappear in time, it is not clear which women on the waiting list for transplantation have been sensitized to paternal HLA antigens and are at risk for graft rejection if paternal HLA antigens are shared by the donor organ. The presence of primed CTLs specific for a particular antigen is considered to be a reflection of sensitization.In the present study we investigated whether these primed CTLs persist in women who had been pregnant and had formed antibodies against the inherited paternal HLA class I antigens. For this purpose 14 women who had their last pregnancy 10 years ago were analyzed with respect to IPA-specific CTLp frequencies and the presence of high avidity CTLs directed against inherited paternal HLA class I antigens. Although primed CTLs specific for IPA's were found more frequently in women with persisting alloantibodies, they still can be detected when the antibodies have disappeared. The current data show that primed CTLs directed against inherited paternal HLA antigens towards which antibodies have been formed in the past can persist for more than 10 years after pregnancy. The cellular test used in our study can be useful to detect presensitization in women with a history of pregnancy, who enter the waiting list for transplantation.