SUPPRESSION OF ALLOANTIGEN-INDUCED T-CELL PROLIFERATION BY CD14(-COLONY-STIMULATING FACTOR-MOBILIZED PERIPHERAL-BLOOD MONONUCLEAR-CELLS() CELLS DERIVED FROM GRANULOCYTE)

The proliferative responsiveness of granulocyte colony-stimulating fac tor (G-CSF)-mobilized blood was studied in uni-directional mixed leuko cyte cultures. Unfractionated mononuclear cells from mobilized blood o btained by leukapheresis at day 4 after initiation of G-CSF (G-PBMC) w ere hyporesponsive (31.5%+/-9.2% response, P=.003) compared to mononuc lear cells obtained from the peripheral blood before administration of G-CSF (preG-PBMC). There was great variability among donors when puri fied preG- and G-CD4 cells were compared, In eight of 10 donors, G-CD4 cells were equally responsive or moderately hyporesponsive; in two of 10 donors, G-CD4 cells were more strikingly hyporesponsive, CD14 cell s derived from leukapheresis products (G-CD14 cells) suppressed alloan tigen-induced proliferation by 48.6%+/-7.5% when added to preG-PBMC or preG-CD4 cells at responder-CD14 ratios of 2:1 (P <.001). Suppression was evident (14.4%+/-5.0%) even at responder-CD14 ratios of 8:1 and w as largely contact-independent. PreG- and G-CD14 cells had equivalent potency in suppressing proliferative responses. Given that G-CSF-mobil ized blood cell grafts contain 50-fold more CD14 cells and only 10-fol d more T cells than marrow, we propose that suppression of donor T cel ls by the large proportion of monocytes present in leukapheresis produ cts could contribute to the unexpectedly low incidence and severity of graft-versus-host disease after peripheral blood stem cell transplant ation. (C) 1997 by The American Society of Hematology.