THE EXPRESSION OF ICAM-1 ON MACROPHAGES STIMULATED WITH MYCOBACTERIUM AVIUM COMPLEX AND ITS CONTROL BY SOME REGULATORY CYTOKINES

Abstract

The interaction of LFA-1 on T lymphocytes with ICAM-1 on antigen presenting cells (APCs) is critical in determining conjugate formation between the APCs and T cells as well as activation of T cells. Recently, it was found that stimulation of THP-1 cells, a human monocyte/Mφ cell line, with Mycobacterium tuberculosis or its lipoarabinomannan, elicited the increase in the ICAM-1 expression. In addition, in cases of lepromatous leprosy patients with a serious defect in the M. leprae antigen-specific cellular immunity, keratinocytes in the leprosy lesions were lacking in the ICAM-1 expression. Therefore, ICAM-1 seems to participate in the host response to mycobacterial infections. Here, we studied the mode of the expression of ICAM-1 molecules on murine peritoneal MφS in response to stimulation with M. avium complex (MAC). In addition, the regulatory effect of some cytokines including TNF-α, IL-10, and transforming growth factor-β (TGF-β) on the ICAM-1 expression was studied.
Monolayer cultures of peptone-starch induced murine peritoneal Ms were cultured in RPMI-1640 medium in the presence of MAC with or without test agents. At intervals, the MO s were stained with anti-ICAM-1 antibody (Ab) and then treated with alkaline phosphatase (Ap)-conjugated anti-Ig Ab. After color development with NBT-BCIP substrate, percentage of the blue-stained (ICAM-1 positive) Mφs was determined microscopically.
The concentrations of TNF-α, IL-10, and TGF-β in the Mφ culture fluid was measured by ELISA using capture Ab, biotin-labelled capping Ab, and Ap-conjugated streptavidin.
When Mφs infected with MAC organisms were cultured in RPMI medium containing 10% fetal bovine serum or in serum-free GPI medium, a significant increase in their ICAM-1 expression was observed, reaching the peak at days 1 to 3, thereafter rapidly de creased and returned to the normal level by day 14. Further addition of TNF-α caused no significant change in the mode of the MAC-induced expression of ICAM-1. A transient increase in the IL-10 production of MAC-infected Mφs was observed during the first 3 days cultivation, as in the case of TNF-α. On the other hand, TGF-β production of the Mφ population was initiated from day 3, and thereafter increased gradually until day 14. ICAM-1 expression of the MAC-infected Mφs was not influenced by the addition of IL-10, while anti-IL-10 Ab retarded the decline of ICAM-1 expression at day 7. On the other hand, the addition of TGF-β attenuated the MAC infection-induced increase in the ICAM-1 expression significantly. In addition, anti-TGF-β Ab significantly delayed the reduction of the ICAM-1 expression of MAC-infected Mφs during days 3 to 7. These results indicate that, in the MAC-infected Mφs, TGF-β rather than IL-10 play important roles as a mediators for the late-phase downregulation of ICAM-1 expression which had been transiently elevated by the action of TNF-α in the early phase of the Mφ cultivation.