To test the efficacy of poststorage bedside leucodepletion of blood products in the prevention of primary HLA alloimmunization and its clinical sequelae, 172 patients with hematologic malignancy requiring intensive red blood cell and platelet support were randomized to receive either standard or filtered red blood cells and platelets. Quality control of bedside filtration was explored by sequential sampling downstream of the filter, but this did not predict the total number of leucocytes transfused. After exclusions, 123 evaluable patients were assessed every two weeks until the end of therapy. HLA antibodies developed in 21 of 56 (37.5%) nonfilter (NF) and 15 of 67 (22%) filter (F) patients (risk ratio estimate, 0.60 [95% confidence interval, 0.34 to 1.05]; P = .07). Patients with acute myeloid leukemia (AML; n = 53) had higher alloimmunization rates in both arms of the study, with a greater effect of filtration (62.5% NF and 31.0% F; P = .025). Bedside filtration did not affect the overall incidence of febrile transfusion reactions (FTRs; 37% NF and 34% F; P = .71) or of platelet refractoriness assessed in 50 patients (30% NF and 26% F), despite an association between broad HLA reactivity and both FTRs and refractoriness. However, FTRs were also seen in 28 patients without HLA antibodies. Five alloimmunized refractory patients (2 F and 3 NF) required HLA-selected platelets. This report, the first prospective study of bedside filtration, has failed to show clear clinical benefit. Methodological limitations may account in part for this failure, notably the difficulties in accurately assessing the number of leucocytes transfused.

No abstract

While the cellular sources for granulocyte-macrophage colony- stimulating factor (GM-CSF) are known to be widely distributed among several cell types, interleukin-3 (IL-3) gene expression has been demonstrated in only certain T-cell clones and in blood mononuclear cells stimulated with phytohemagglutinin (PHA) and phorbol-myristate- acetate (PMA). To determine which blood cells were responsible for this expression, we fractionated PHA/PMA-stimulated mononuclear cells and identified T lymphocytes as the source of IL-3 mRNA. Low-level IL-3 expression was detected as well in several stimulated human T-cell lines. Hematopoietic stromal cells such as fibroblasts and endothelial cells could not be induced to express IL-3 mRNA. The kinetics of IL-3 mRNA induction in mononuclear cells and lymphocytes stimulated with PHA/PMA or anti-CD3 monoclonal antibody (MoAb) and interleukin-1 (IL-1) were similar to those observed for GM-CSF expression.

While the cellular sources for granulocyte-macrophage colony- stimulating factor (GM-CSF) are known to be widely distributed among several cell types, interleukin-3 (IL-3) gene expression has been demonstrated in only certain T-cell clones and in blood mononuclear cells stimulated with phytohemagglutinin (PHA) and phorbol-myristate- acetate (PMA). To determine which blood cells were responsible for this expression, we fractionated PHA/PMA-stimulated mononuclear cells and identified T lymphocytes as the source of IL-3 mRNA. Low-level IL-3 expression was detected as well in several stimulated human T-cell lines. Hematopoietic stromal cells such as fibroblasts and endothelial cells could not be induced to express IL-3 mRNA. The kinetics of IL-3 mRNA induction in mononuclear cells and lymphocytes stimulated with PHA/PMA or anti-CD3 monoclonal antibody (MoAb) and interleukin-1 (IL-1) were similar to those observed for GM-CSF expression.

Northern blot analysis has identified granulocyte macrophage colony stimulating factor (GM-CSF) mRNA in monocytes and both GM-CSF and interleukin-3 (IL-3) mRNA in lymphocytes. However, these results have not addressed whether all cells or a subset of the population is capable of hematopoietic growth factor (HGF) production. To resolve this question, we applied in situ hybridization of radiolabeled antisense RNA probes to centrifuged preparations of total blood mononuclear cells (BMCs) and fractionated lymphocyte subpopulations. Without stimulation, no circulating cells expressed detectable levels of GM-CSF or IL-3 mRNA. On stimulation of BMCs with phorbol myristate acetate (PMA) and phytohemagglutinin or PMA and the calcium ionophore ionomycin, approximately 5% expressed GM-CSF mRNA and approximately 1% IL-3 mRNA. Control sense probes produced no labeled cells. To determine the subsets of lymphocytes capable of GM-CSF and IL-3 expression, BMCs were fractionated by FACS into CD8+ and CD4+ lymphocyte subsets and CD16+ (NK) cells. The unfractionated cells and cell fractions were then stimulated with PMA and ionomycin. Results demonstrated that 3% to 5% of the CD16+, CD8+, and CD4+ lymphocytes produced GM-CSF mRNA. However, the number of IL-3 mRNA-positive cells in the FACS-sorted subsets was greatly reduced (0.02% to 0.05%) as compared with the unseparated cells (1%). Treatment of BMCs with high-dose interleukin-2 (IL-2) for 1 week followed by PMA plus ionomycin resulted in a lymphocyte population in which 50% and 3% of cells expressed GM-CSF and IL-3 mRNA, respectively. Thus, GM-CSF and IL-3 mRNA expression in T cells and NK cells is restricted to a small fraction of cells that can be greatly expanded by IL-2 stimulation. These results suggest a possible physiologic mechanism for increasing HGF production by circulating lymphocytes.