TRANSFUSION-ASSOCIATED GRAFT-VERSUS-HOST DISEASE IN IMMUNOCOMPETENT PATIENTS - A SELF-PROTECTIVE MECHANISM

Transfusion-associated graft-versus-host disease (TA-GVHD) is a rare but hazardous complication caused by transfusion of leucocyte-containing blood. It is not clear why some patients are at risk for TA-GVHD, but others are not. We studied TA-GVHD in immunocompetent individuals by looking at donor-anti-host reactivity after transfusion of leucocyte-containing blood. We tested reactivity in 62 donor-recipient combinations in vitro before and at different times after blood transfusion with mixed lymphocyte culture. One patient was studied in more detail. Reactivity of blood donors against hosts gradually decreased after blood transfusion. This decrease significantly correlated with time (p<0.001). Studies in a single patient showed that absence of donor-host reactivity was due to host T cells that inhibited the response. These data indicate that an active mechanism exists in immunocompetent individuals which inhibits the graft-versus-host reaction of the donor against the host. This mechanism might be exploited in organ transplantation by pre-transplant blood transfer.