The neonatal immune response to washed and irradiated red cells: lack of evidence of lymphocyte activation

A total of 21 neonatal infants (11 males and 10 females) were evaluated for lymphocyte subpopulation changes and cellular activation following the receipt of washed and gamma-irradiated red cells. The mean donor exposure was 2 +/- 1.5 donors, and the mean white cell concentration of each 10-mL-per-kg transfusion was 2 x 10(7) cells. A total of 2800 rad (28 Gy) was delivered to each red cell unit prior to washing. The lymphocyte subsets CD3+, CD4+, CD8+, CD19+, CD3+/CD25+, CD3+/HLA-DR, CD4+/CD45RA, CD4+/CDw29, and CD4+/ICHL-1 were analyzed, as were plasma gamma-interferon and neopterin levels, before and after blood transfusion. Posttransfusion samples were obtained from 3 to 12 days after the last blood transfusion. There were no posttransfusion changes in the percentage of lymphocyte subsets analyzed. Furthermore, overlay-histogram analysis of pretransfusion and posttransfusion CD45RA-, CDw29-, and UCHL-1-positive helper T cells failed to reveal a shift in mean channel fluorescence intensity, which is indicative of a lack of cellular activation. Gamma-interferon levels remained unchanged after transfusion (range, 90 +/- 5.9 to 95.5 +/- 5.3 pg/mL), as did neopterin levels (range, 3.7 +/- 1.5 to 4.6 +/- 1.5 ng/mL). This study could not find any evidence, by either cellular or humoral markers, of the activation of neonatal lymphocytes by transfusion. It is hypothesized that this failure to observe lymphocyte activation is due to the low number of donor white cells present in washed, irradiated red cells and/or to a lack of recipient recognition of transfused, allogeneic, donor white cells.