マクロファージのIL-12産生を高値に誘導する結核菌体成分の解析 ANALYSIS OF MYCOBACTERIUM TUBERCULOSIS-DERIVED SUBSTANCE WHICH INDUCES INTERLEUKIN-12 PRODUCTION FROM MACROPHAGES
rotection of hosts against tuberculosis depends on expression of cellular immunity. To express cellular immunity, interleukin-12 (IL-12) has been shown to play an important role. Although Mycobacterium tuberculosis is known to induce IL-12 from macrophages (Mφs), the mechanism for the induction is still unclear.<BR>To understand the mechanisms of IL-12 induction from Mφs by M. tuberculosis, the IL-12 inducing ability of substances derived from M. tuberculosis was investigated in vitro. Production of IL-12 in culture medium of Mφs was measured by ELISA system using specific antibodies. Live M. tuberculosis H37Rv induced slightly higher IL-12 production than live M. tuberculosis H37Ra upon stimulation of human or mouse alveolar macrophages (hAMφs or mAMφs). Heat-killed M. tuberculosis failed to induce IL-12 production of alveolar macrophages (AMφ). The responses of hAMφs and mAMφs to M. tuberculosis were remarkably different. mAMφs produced five times larger amount of IL-12, compared with that from hAMφs. Human peripheral blood mononuclear cells (PBMC) obtained by the density gradient centrifugation were also used for induction of IL-12production. Although production levels of IL-12 from PBMC stimulated with M. tuberculosis were below the detectable level, addition of interferon- γ (IFN-γA) or neutralizing antibody against IL-10 augmented the production of IL-12 from PBMC, suggesting that IFN- γ and IL-10 regulate the production of IL-12 from Mφ positively and negatively, respectively.<BR>To characterize the physicochemical properties of IL-12-inducing molecules, M. tuberculosis H37Rv was disrupted by pressing with 1, 000 bar and centrifuged and separated into cytosol and cell wall fraction. The culture filtrate was also examined on IL-12-inducing activity. Among the three subjects examined, cytosol was found to induce the highest production of IL-12 from mAMφs 1 day after the stimulation. Addition of IFN- γ to the cytosol fraction markedly increased the production of IL-12 from mAMφs. The molecular weight of IL-12-inducing substance was shown to be more than 30kDa by fractionating with molecular filters. Treatment of 30kDa-fraction with IL-12-inducing activity by proteinase K completely abolished the activity. Furthermore, approximately 90% of IL-12-inducing activity of 30kDa-fraction was lost by proteinase K treatment even in the presence of IFN-γ. These results indicate that the major component of IL-12-inducing activity is a protein. The identification of this IL-12-inducing active substance may provide a new therapeutic tool for tuberculosis.
結核 73(9), 531-543, 1998-09-15
JAPANESE SOCIETY FOR TUBERCULOSIS