WHY USE LEUKOCYTE-POOR BLOOD COMPONENTS I N 1995

During the last 15 years, the techniques to prepare leukocyte-poor cel lular blood components greatly improved, as well as our knowledge abou t the role of leukocytes in many adverse effects of transfusion. These two facts favor the extension of indication of leukocyte-poor blood c omponents. Leukocytes in blood components may be detrimental to their storage, due to their metabolic needs and to their progressive lysis, leading to the release of cytokines. Leukocytes are the exclusive vect or in blood of CMV and HTLV viruses. Leukocytes are a key element of t he immune modifications induced by transfusion. HLA alloimmunization i s favored by the transfusion of large quantities of leukocytes HLA dif ferent from the recipient whose immune functions are intact. Conversel y, the risk of transfusion associated graft versus host disease is dep endent of the transfusion of mature T lymphocytes sharing a partial id entity with the recipient, and/or an immune deficient status of the re cipient. Between these two extremes, many other effects related to the presence of leukocytes in cellular blood components, as are the trans fusion effect observed in transplant recipients, the increased risk fo r bacterial infection after transfusion, the increased risk for turner recurrence or the reactivation of virus infections, remain to be full y understood. Despite recent significant improvements, further studies , experimental as well as clinical, will be needed to expand the indic ations of leukocyte-poor blood components.