Monocytes from mobilized stem cells inhibit C cell function

Abstract

Granulocyte-macrophage colony-stimulating factor, mobilized peripheral blood stem cell (PSC) products, and peripheral blood leukocytes posttransplantation contain cells that cause allogeneic and autologous T cell apoptosis. Isolation and characterization of these cells demonstrated that they were low-density (Percoll fractionation) CD14+ monocytes. T cells in PSC products have a depressed phytohemagglutinin (PHA) mitogenic response; however, purified CD4+ or CD8+ T cells exhibit a statistically normal mitogenic function. Furthermore, no T cell inhibitory activity was observed in CD14+, CD4+, and CD8+ cell-depleted fractions enriched in CD4- CD8- TCRα/β+ T cells. Inhibition of T cell function by CD14+ monocytes required cell-cell contact, and the analyses of DNAS fragmentation by Southern and TUNEL analysis demonstrates an activation-induced T cell apoptosis in the presence of CD14+ monocytes. Reverse-transcriptase polymerase chain reaction studies suggested that high levels of interleukin-10 or tumor necrosis factor gene transcripts in the PSC products may contribute to the inhibition of T cell function.