USE OF LEUKODEPLETION FILTERS FOR THE REMOVAL OF BACTERIA

Recipient exposure to allogeneic donor leukocytes can mediate a number of immunologic complications of transfusion or can transmit leukotrop ic viruses carried by the donor. Leukocyte depletion of cellular blood components has been shown to reduce the incidence of such complicatio ns. In recent years, prestorage leukocyte depletion by filtration has also been suggested as a means of decreasing the incidence of bacteria l overgrowth in cellular blood components. This review analyzes publis hed studies on the use of leukodepletion filters for removal of Staphy lococcus epidermidis and Yersinia enterocolitica from blood. Although ineffective for removal of S. epidermidis from Platelet Concentrates, inoculation studies demonstrate removal of low levels of Y. enterocoli tica from Red Cell Concentrates. Based on these studies, four possible mechanism(s) for removal of bacteria by leukodepletion filters are an alyzed: phagocytosis by leukocytes during a prefiltration holding peri od; complement-mediated bacterial killing enhanced by filtration; adhe rence of bacteria to leukocyte surfaces retained within the filter; an d direct removal of bacteria by the filter media. Just as multiple mec hanisms appear to account for the efficiency with which these filters deplete blood of leukocytes, it is likely that more than one mechanism accounts for the experimental observation that leukocyte depletion fi lters can reduce overgrowth of Y. enterocolitica in stored Red Cell Co ncentrates.