PROCESSING AND PRESENTATION OF AN ANTIGEN OF MYCOBACTERIUM-AVIUM REQUIRE ACCESS TO AN ACIDIFIED COMPARTMENT WITH ACTIVE PROTEASES

We have generated a murine T-cell hybridoma, 1C9, which recognizes an antigen expressed by a virulent clinical isolate of Mycobacterium aviu m. Both peritoneal exudate macrophages and bone marrow-derived macroph ages infected in vitro with M. avium process and present the antigen t o the T-cell hybridoma, Gel filtration chromatography of a sonicate of M. avium followed by T-cell Western blotting (immunoblotting) demonst rated that the antigen recognized by hybridoma 1C9 is approximately 50 kDa. In addition, treatment of macrophages with the lysosomotropic ag ent chloroquine or with inhibitors of acid proteases inhibits processi ng and presentation of the antigen, These results indicate that the an tigen must encounter an acidic compartment with active proteases for p rocessing and presentation to occur. Our results are discussed in the context of our current understanding of how mycobacterial antigens are processed and presented by infected macrophages to T cells.