Studies on Antigens Associated with the Activation of Murine Mononuclear Phagocytes: Kinetics of and Requirements for Vitro' Induction of Lymphocyte Function-associated (lfa)-1 Antigen In

Macrophages activated and primed in vivo, although not resident or responsive macrophages, express the lymphocyte function associated (LFA)-1 antigen. By contrast, the biochemically related Mac1 antigen is expressed on all populations of macrophages. In the present paper, we studied regulation of the LFA-1 antigen in vitro. LFA-1 could be induced in vitro n thioglycollate (TG)-elicited but not on proteose peptone (PP)-elicited or resident macrophages. Specifically, macrophage-activating factor (MAF), interferon-y (IFN-7). or picogram amounts of endotoxin (LPS) induced LFA-1 on TG-elicited macrophages following overnight incubation. Interferon, -a or -& fucoidin, and colony-stimulating factor were not effective. While some levels of LFA-1 could be detected as soon as 10 hr, peak expression was observed after 16 to 32 hr of incubation. The induction could be completely abrogated by cycloheximide, suggesting that protein synthesis was required. These results indicate that the induction of LFA-1 on mononuclear phagocytes is closely regulated and that the requirements for such induction are distinct from but share certain similarities with induction of cytotoxic functions and expression of Ia antigen.