Abstract：The present study was aimed to investigate major histocompatibility complex Ⅱ ( MHC Ⅱ ) antigen presentation induced by interferon-γ ( IFN-γ) in macrophages after exposure to Mycobacterium tuberculosis ( M. uberculosis) . The expressions of MHCⅡ, CD86, and CD80 on macrophages, after exposure to M. tuberculosis for 24 h prior to the addition of IFN-γ, were detected by flow cytometry. The mRNA levels of CⅡTA, PⅠ, PⅢ and PⅣ were assayed by reverse transcriptase-polymerase chain reaction. MHCⅡ antigen presentation was detected by enzyme-linked immunosorbent assay ( ELISA) . The results showed that M. tuberculosis inhibited the expressions of MHCⅡ and CD86 but not CD80 induced by IFN-γon macrophages. The ability of antigen presentation was also inhibited. The mRNA levels of CⅡTA, PⅠ, PⅢ and PⅣ induced by IFN-γwere also decreased. It suggests that M. tuberculosis inhibits MHCⅡ antigen presentation induced by IFN-γon macrophages.