Interleukin-10 Contributes Development of Macrophage Suppressor Activities by Macrophage Colony-Stimulating Factor, But Not by Granulocyte–Macrophage Colony-Stimulating Factor

Macrophages are known to possess suppressor activities in immune responses. To determine the effects of GM-CSF and M-CSF on the expression of macrophage suppressor activities, monocyte-derived macrophages cultured with GM-CSF (GM-Mφs) were compared with those cultured with M-CSF (M-Mφs) for antigen-specific proliferation and interferon-γ (IFN-γ) production by lymphocytes. Both GM-Mφs and M-Mφs equally suppressed lymphocyte proliferation, but only M-Mφs suppressed IFN-γ production in response to purified protein derivative (PPD). M-Mφs, but not GM-Mφs, released IL-10 not only in the course of macrophage differentiation but also in response to PPD after maturation to macrophages. From the results that (i) exogenous IL-10 suppressed IFN-γ production, but not proliferation of lymphocytes, and that (ii) neutralizing antibody to IL-10 reversed suppressor activities of M-Mφs on IFN-γ production, but not lymphocyte proliferation, it appeared that IL-10 was the major factor responsible for suppression of IFN-γ production. Thus, these results suggest that only M-CSF augments IL-10-dependent suppressor activity of macrophages on IFN-γ production and that both GM-CSF and M-CSF induce IL-10-independent macrophage suppressor activity on lymphocyte proliferation.