Macrophage suppressor factor in contact sensitivity. Mechanisms of its release and action

An antigen-specific suppressor factor (TSF) produced by mouse T lymphocytes prevents immune cells from conferring adoptive immunity on normal recipients. This TSF attaches easily to the macrophage surface, and these 'armed' macrophages in the presence of a corresponding antigen manufacture (in vitro) a non-specific macrophage suppressor factor (MSF) which impairs the activity of cells sensitized to homologous or heterologous antigens. Our experiments show that MSF is temperature- and trypsin-sensitive, and is not a prostaglandin. Its molecular weight is in the range of 10 kD. MSF is synthesized by macrophages de novo subsequent to triggering by TSF and antigen. MSF impairs only the activity of cells mediating contact sensitivity reaction (Ly 1) but has no influence on T-suppressor cells (Ly 23). The possibility that MSF is an enzyme is discussed.