Suppressed induction of mycobacterial antigen-specific Th1-type CD4+ T cells in the lung after pulmonary mycobacterial infection

Although the importance of Th1-type immune response in protection against mycobacterial infection is well recognized, its regulatory mechanism in the Mycobacterium tuberculosis (Mtb)-infected lung is not well characterized. To address this issue, we analyzed kinetics of induction of mycobacterial antigen-specific CD4 1 Th1 T cells after mycobacterial infection in P25 TCR-transgenic (Tg) mice which express TCR a and b chains from a mycobacterial Ag85B-specific MHC class II A b -restricted CD4 1 T-cell clone. To supply normal regulatory T-cell repertoire, we transferred normal spleen T cells into the P25 TCR-Tg mice before infection. High dose subcutaneous infection with Mtb or Mycobacterium