Corynebacterium parvum- and Mycobacterium bovis Bacillus Calmette and Guerin-induced granuloma formation in mice lacking CD4 and CD8

Granuloma formation is a T-cell-dependent inflammatory response that is important in the host defense against intracellular bacteria. The role of CD4 and CD8 molecules in the development of Corynebacterium parvum- and Mycobacterium bovis Bacillus Calmette and Guerin (BCG)-induced granulomas was examined in CD4/CD8 knockout (KO) mice. CD4/CD8 KO mice developed a greater granulomatous response to heat-killed C. parvum and heat-killed BCG than did control mice. Thus, granuloma formation is not dependent upon the presence of CD4 and CD8. On the other hand, CD4/CD8 KO mice challenged with live BCG showed initially fewer and smaller granulomas but later more and larger granulomas than control mice. CD4/CD8 KO mice had a greater BCG load than control mice. The absence of CD4 and CD8 therefore impaired the host defense against infection with BCG. alphabeta T-cells were present in the granulomas of both CD4/CD8 KO and control mice in similar numbers. Also the production of IFN-gamma mRNA was similar in the two groups. In conclusion, CD4 and CD8 are not essential to the granulomatous response against C. parvum and BCG, but contribute to the host defense against live BCG infection.