Murine T helper cell clones secrete granulocyte-macrophage colony-stimulating factor (GmCSF) by both interleukin-2-dependent and interleukin-2-independent pathways

Granulocyte-macrophage colony-stimulating factor (GmCSF) is a lymphokine secreted by class II major histocompatibility complex (MHC)-restricted T cells after lectin or antigen stimulation. To investigate the relationship between interleukin-2 (IL-2) and GmCSF production, we utilized long-term cultures of porcine myelin basic protein (PMBP)-specific T helper cell clones that were maintained with IL-2 in the absence of antigen or irradiated antigen-presenting cells (APC). We have found that supernatants of these T cell clones contained GmCSF activity after IL-2 stimulation. Inhibition of cell proliferation by irradiation failed to stop GmCSF production. When these clones were stimulated with PMBP and irradiated APC in the presence of anti-IL-2 receptor antibody, the T cell supernatants still contained GmCSF activity. These results indicate that (1) GmCSF production by T helper clones after IL-2 stimulation is independent of cell proliferation and (2) antigen/MHC-stimulated GmCSF production by T cell clones can occur by an IL-2-independent pathway.