Activation of lymphocytes after platelet allotransfusion possessing only class I MHC product
After platelet allotransfusion, we found a characteristic increase in the expression of interleukin‐2 receptor, dipeptydilpeptidase IV (CD26), activation‐inducer molecule (AIM, CD69) and transferrin receptors (CD71) on day 3 indicating that important functional molecules expressed on the activation of lymphocytes by allogeneic platelets. At the same time, no consistent increase of other activation molecules such as Ki‐1 (CD30), intercellular adhesion molecule (ICAM‐1, CD54) and Ki‐24 (CDw70) antigen expression was detected, probably as a result of the selective activation of some lymphocyte subsets. In order to obtain further evidence for the in vivo activation triggered by allogeneic platelets, a subsequent step of T cell activation towards differentiation was investigated with monoclonal antibodies to leucocyte common antigens. A sharp expression of the UCHL1, coupled with a decrease of the CD45R molecule was detected on day 7 or 14, suggesting a T cell priming.