Characterization of a New Human Macrophage Cell Line 2MAC

A human macrophage-like line, designated SMAC, has been established from peripheral blood. 2MAC expresses a number of lineage-specific markers as well as a broad array of intercellular adhesion molecules. In particular, 2MAC expresses CD16/Fc gamma RIII, the low-affinity Fc receptor for IgG, as well as high levels of HLA class I and class II. Consistent with this macrophage assignment, we present evidence that 2MAC expresses the macrophage form of CD16, namely, Fc gamma RIIIA/gamma. By several criteria also applicable to signal transducing NK CD16 and T cell CD3/TCR complexes, including modulation from the cell surface and Ca2+ mobilization in response to ligation by specific monoclonal antibody, CD16 expressed by SMAC is functional. Ligation of 2MAC HLA class II, but not HLA class I, by specific mAb induces an increase in free cytoplasmic Ca2+ concentration ([Ca2+](i)). This Ca2+ flux appears to be physiologically relevant, as ligation of HLA-DR, but not HLA class I, by mAb results in the efficient, Ca2+ mobilization-dependent induction of tissue factor by SMAC. 2MAC, therefore, should prove useful for studying signal transduction through macrophage CD16 and HLA class II. (C) 1997 Academic Press.