Roles of tumour necrosis factor-alpha (TNF-α), transforming growth factor-beta (TGF-β), and IL-10 in the modulation of intercellular adhesion molecule-1 (ICAM-1) expression by macrophages during mycobacterial infection

Profiles of ICAM-1 expression on cultured murine peritoneal macrophages infected with Mycobacterium avium complex (MAC) were examined, with special reference to modulating roles of TNF-α, TGF-β, and IL-10. When macrophages were infected with MAC, ICAM-1 expression, measured by microscopic counting of ICAM-1⁺ macrophages stained with anti-ICAM-1 antibody, ELISA, and flow cytometric analysis, was rapidly increased, peaking at day 3 (early-phase up-regulation) due to endogenous TNF-α, and thereafter gradually declined to the normal level within 1 week or more (late-phase down-regulation). The late-phase ICAM-1 down-regulation was also seen in macrophages phagocytosing heat-killed MAC and those stimulated with lipopolysaccharide but not in macrophages phagocytosing latex beads. ICAM-1 mRNA expression was augmented markedly at day 1 after MAC infection and thereafter decreased. While TNF-α and IL-10 production by MAC-infected macrophages was observed during the first 3 days, TGF-β production was initiated from day 3 and continued until day 14. Exogenously added TGF-β strongly inhibited the early-phase increase in ICAM-1 expression by infected macrophages, and the blockade of endogenous TGF-β with anti-TGF-β antibody markedly inhibited late-phase ICAM-1 down-regulation. Moderate blocking effect was also observed for anti-IL-10 antibody. On the other hand, late-phase ICAM-1 down-regulation was not prevented by the addition of exogenous TNF-α. Therefore, TGF-β and IL-10, especially the former, appear to play active roles in the late-phase down-regulation of ICAM-1 in MAC-infected macrophages during long-term cultivation.