Selective chemotaxis of Ia antigen-positive macrophages by macrophage chemotactic lymphokine produced by concanavalin A stimulation

M1^- cells (leukaemic cell line cells established from SL/Am mouse), Mm1 cells (macrophage-like subcloned from M1^- cells), and undifferentiated B24 cells (subcloned from M1^- cells) were similarly Ia-negative and showed little chemotactic response to macrophage chemotactic lymphokine (MCF-LD) produced by Con A stimulation of spleen cells. However, when M1^- cells and B24 cells were differentiated by differentiating factor in the fibroblast-conditioned medium, they became positive for surface Ia antigens and exhibited chemotactic response to MCF-LD. Treatment of the cell-line cells and mouse peritoneal exudate macrophages with anti-Ia antiserum and complement reduced the number of cells responsive to MCF-LD. Moreover, when comparing the chemotactic responses to MCF-LD of Ia-negative and Ia-positive peritoneal exudate macrophages, separated by electric programmable individual cell sorter (EPICS), Ia-positive cells responded more strongly than Ia-negative cells.