T cell regulation of myelopoiesis: analysis at a clonal level

Colony-stimulating factor (CSF) production by a series of cloned human T lymphocyte cell lines was examined by substituting cloned T cells for peripheral blood mononuclear cells in the feeder layer of a double-layer agar CFU-C assay system. Of 12 T cell lines tested, all produced CSF when stimulated by specific antigen, whereas CSF production in the absence of stimulation was generally negligible. In the case of soluble antigen-specific (ragweed or tetanus toxoid) clones, this required both nominal antigen and the appropriate MHC gene product on autologous antigen-presenting cells, whereas in the case of clones specific for EBV-transformed B cell lines (allogeneic or autologous), surface-bound EBV-related antigen and MHC was necessary. When tested in this manner, CSF production by different cloned T cells was heterogeneous in both amount and subclass. Thus, although most clones stimulated growth of granulocyte, monocyte, and eosinophil colonies, certain clones were identified which preferentially stimulated some colony types but not others. This heterogeneity was particularly evident with respect to eosinophil colony production. In addition, a soluble inhibitor of granulocyte colony growth was produced by one clone. These findings provide further support for the notion that antigen-specific T cells may, on activation, regulate myelopoiesis in a precise way, and provide a possible cellular basis for selective eosinophilia, monocytosis, or neutrophilia seen in certain disease states.