[Effect of natural resistance gene on the immune response against Mycobacterium avium complex infection]

Natural resistance gene (Bcg) is mapped to chromosome # 1 and known to control the host resistance against Mycobacterium avium Mino infection in mice. Using two sets of Bcg-congenic mice, BALB/c vs C.D2 and B10.A vs B10.A.Bcgr, we determined phenotypic differences in macrophages between Bcgs and Bcgr. Bcg gene product is not detected yet but thought to be expressed in macrophages and should be effective in mycobacteria-killing mechanisms of the host macrophages. It was found that AcM.1 expression is higher in Bcgr than Bcgs, while O2- production and granuloma formation are stronger in Bcgs than Bcgr. Cytokine messages were detected in Mino-infected macrophages. TNF is produced more in Bcgs, while IL-6 is higher in Bcgr. IL-1 was almost the same in both strains. Exogenous cytokines, IL-4 or IFN-r, added to the culture of Mino-infected macrophages, enhanced the bacteria killing in Bcgr but not in Bcgs.