Regulation of enzyme secretion by mononuclear phagocytes: studies with macrophage plasminogen activator and lysozyme.

Lysozyme and plasminogen activator (PA) are independently regulated secretion products of the macrophage. Lysozyme is released constitutively by all types of macrophage, whereas PA is induced during macrophage activation by nonspecific stimuli or by an immunologically specific pathway under control of sensitized T lymphocytes and antigen. Production of PA is closely related to the ability of the macrophage to proliferate in the presence of colony stimulating factor (CSF). Production of lysozyme is often extinguished after hybridization of macrophages with other cells, but may persist and serve as a useful marker for expression of the differentiated macrophage phenotype in somatic cell hybrids.