[Lymphocyte interactions in platelet concentrates from buffy coats. Determination of proliferating cells using Ki-67...

The preparation of platelet concentrates (PC) from pooled buffy coats has raised concern as to whether activation of lymphocytes may take place during the period of storage. Lymphocytes and HLA-DR-positive cells are of particular relevance, as they may induce a mixed lymphocyte reaction (MLR). Therefore we investigated the degree of leukocyte contamination and determined the quantity of proliferating leukocytes using the monoclonal antibody KI-67. The content of total leukocytes was (0.07 +/- 0.05) x 10(9). Immunostaining of KI-67-positive cells proved that, directly after preparation, only single leukocytes were activated. On days 1, 3 and 5 after preparation the results were identical. Isolated cells were found to be KI-67-positive but there was no significant increase in proliferating cells as would have been expected in an MLR. We conclude that there is no allogenic activation of lymphocytes taking place in these PC during storage. Therefore transfusion of activated lymphocytes seems to be extremely unlikely.