Cytokine mRNA and protein expression in a mixed leukocyte reaction before and after allogeneic transfusions

Background. The precise mechanism by which pretransplant blood transfusions may favorably influence the graft outcome in human transplantation remains unknown. Here, we explored whether the mechanism might be related to an alteration of cytokine response to transplantation antigens. Methods. Eight patients awaiting kidney transplantation were selected to receive a single planned pretransplant blood transfusion. Before transfusion and 7 days after transfusion, peripheral blood mononuclear cells from these patients were isolated and in vitro stimulated in a one-way mixed leukocyte reaction (MLR) by using allogeneic fixed Epstein Barr virus-transformed cells as stimulators. Results. The use of a semiquantitative reverse-transcriptase polymerase chain reaction cycle technique to analyze cytokine mRNAs revealed that allostimulation by donor cells clearly induced accumulation of interleukin (IL)-2, IL-4, interferon (IFN)-gamma, and IL-10 mRNA in peripheral blood mononuclear cells collected both before and after transfusion (eight of eight patients). However, both T helper 1 (IFN-gamma) and T helper 2 (IL-4) cytokine responses were more elevated after transfusion in eight of eight patients, as were IL-2 responses in five of eight patients. Such up-regulation of cytokine responses by transfusion was mostly directed against blood donor cells. Indeed, after stimulation by third-party cells, this up-regulation was both inconstant (two of three patients) and of less intensity, and no change was detected after stimulation by autologous cells (three of three patients). Conclusions. That IL-2, IL-4, and IFN-gamma responses to donor cells were increased by transfusion was further supported by results on cytokine secretion showing increased levels of IL-2 (P<0.05), IFN-gamma (P=0.054), and IL-4 (P<0.05) proteins in supernatants of posttransfusion MLR as compared with pretransfusion MLR. In contrast, transfusion-induced changes in the amount of IL-10 mRNAs were not obvious and were quite variable from one patient to another.