PREVENTION OF DONOR-SPECIFIC T-CELL UNRESPONSIVENESS AFTER BUFFY-COAT-DEPLETED BLOOD-TRANSFUSION

The immunosuppressive effect of blood transfusions has been demonstrat ed in several clinical studies. The effect is probably mediated by HLA -class-II-bearing donor leucocytes, because results from laboratory te sts show specific down-regulation of the recipient's T-cell response a fter administration of blood from donors sharing one HLA haplotype wit h the recipient. In the present study we evaluated the immunosuppressi ve potential of huffy-coat-depleted red cell transfusions in patients waiting for renal transplantation, by measuring the frequency of cytot oxic precursor T cells before and after transfusion. The buffy coat wa s removed from whole blood by the Optipress system and resulted in >97 % depletion of lymphocytes and monocytes, A single transfusion of HLA- haplotype-matched buffy-coat-depleted red cells induced donor-specific down-regulation of T-cell responses in only two of 14 patients. Since HLA-class-II-bearing cells are also involved in the induction of anti -HLA antibodies, we evaluated retrospectively the incident of HLA allo immunization after a single transfusion of buffy-coat-depleted red cel ls. No anti-HLA antibodies were found in 140 patients at risk for prim ary immunization. We conclude that the poor immunological responses fo und after a single transfusion of HLA-haplotype-matched buffy-coat-dep leted red cells is due to the small number of residual HLA-class-II-be aring donor cells, This blood component should not be used for inducti on of immunosuppression.