Increased IFN-gamma response to transplantation antigens measured by cytokine MLC: indications for a bi-phasic response pattern.

The immunological reactivity to major histocompatibility transplantation antigens (MHC) is important in clinical manifestations such as graft rejection and graft-vs.-host disease. To evaluate the allogeneic cytokine response pattern we used a newly developed cytokine mixed leukocyte culture (MLC) technique. Blood mononuclear cells from healthy women (n=6) were exposed to cells from another person and to pooled cells from 28 blood donors (MHC-pool). The secretion kinetics of IL-4 and IFN-gamma from the responder cells was analysed by ELISPOT. We found a higher IFN-gamma response to the MHC-pool compared with the IL-4 secretion. Both the total secretion of IFN-gamma for 7 days and the median value of IFN-gamma in each individual was increased compared with IL-4. The IFN-gamma response showed a bi-phasic pattern with the major peak on day 6-7. Our results indicate that allo-responses are mainly Th1-like responses, displaying a bi-phasic pattern. This knowledge may be useful, and the methods suitable, in the studies of allo-responses in transplantation and pregnancy.