Target cells for interferon induction by BL-20803.

The role of certain cells of the reticuloendothelial system in the interferon response of mice to the low-molecular-weight compound 1,3-dimethyl-4-(3-dimethylaminopropylamino)-1H-pyrazola-3,4-b-quinoline dihydrochloride (BL-20803) was studied. Mouse spleen adherent cells cultured in vitro with subtoxic concentrations of BL-20803 produced interferon. Adherent cells isolated from peritoneal washes were unresponsive to the compound. Treatment of mice with rabbit antiserum to mouse adherent cells suppressed interferon production by at least 65%, wheras antisera to thymocytes or to nonadherent spleen cells failed to suppress the interferon response. Pretreatment of mice with zymosan resulted in the appearance of circulating interferon in mice given 100 mg of the inducer/kg (a dosage to which they are normally unresponsive). No potentiation of the interferon response to the drug occured in immunized mice actively making a humoral or delayed-type hypersensitivity immune response. It is concluded that a specific type of cell in the mouse, the so-called "fixed macrophage," may be a major target for interferon induction by BL 20803.