A cytotoxic mononuclear phagocytic cell line

Abstract A human mononuclear phagocytic cell line (M22) was established from lymph node cells of a cancer patient. Little or no multiplication occurred in the absence of target cells such as primary or continuous cultures of human, monkey, or mouse. In response to a target stimulus, M22 altered from the resting thick-walled stage and in time, target cells were destroyed. M22 resembled a monocyte, possessing Fc and complement receptors, strong nonspecific esterase activity, pinocytosis, and lacking B- and T-cell markers but differed by lacking lysozyme. It possessed acid and alkaline phosphatases but lacked myeloperoxidase. Unlike other described monocyte lines, M22 was unique in its nonspecific cytotoxic activity.