Change of mouse CD5+ B1 cells to a macrophage-like morphology induced by gamma interferon and inhibited by interleukin-4

The in vitro effects of gamma interferon (IFN-gamma) on the mouse CD5(+) B1-cell line, TH2.52, a hybridoma between mouse B lymphoma and mouse splenic B cells that expresses a series of B1 markers, were investigated. A significant number of macrophage-like cells appeared in the cultures of TH2.52 cells exposed to IFN-gamma, these adhering to plastic dishes and exhibiting phagocytic activity. Positive for esterase staining, the macrophage-like cells returned to the original TH2.52 morphology upon removal of IFN-gamma. The change was prevented by treatment with SB202190, an inhibitor of P38 mitogen-activated protein (MAP) kinase and by transfection of a p38 MAP kinase dominant-negative mutant. Further, interleukin-4 (IL-4) inhibited IFN-gamma-induced phosphorylation of p38 MAP kinase and the appearance of macrophage-like cells. IFN-gamma and IL-4 exhibited contradictory actions on morphological change of D5(+) B1 cells into macrophage-like cells. Differential regulation of CD5(+) B1 cells by IFN-gamma, a Th1 cytokine, and IL-4, a Th2 cytokine, may have clear immunological significance.