[Participation of gamma/delta-T cells in the protection against mycobacterial infection]

To search for a potential role of T cell receptor (TcR) gamma/delta T cells in host-defense against mycobacterial infection, we analyzed the kinetics, repertoire, specificity and function of gamma/delta T cells in the peritoneal cavity, lymph node (LN) and spleen during an intraperitoneal infection with a sublethal dose (5 x 10(5)) of viable BCG in mice. The number of bacteria in the organs increased to a maximal level by 28 days after infection, and thereafter decreased gradually. Of the CD3+ cells in PEC on day 7 after infection, approximately 25% were CD4-CD8-, most of which express TcR gamma/delta on their surface. On the other hand, the PEC on day 28 contained an increased number of alpha/beta T cells which were CD4+CD8- or CD4-CD8+ and the proportion of gamma/delta T cells was reciprocally decreased. The kinetics of gamma/delta and alpha/beta T cells in the LN ad spleen during BCG infection are much the same as that seen in the PEC. The early appearing gamma/delta T cells preferentially used V gamma 1/V delta 6 although the repertoire of these T cells are diversified. The gamma/delta T cells in PEC on day 7 remarkably proliferated and produced gamma IFN and IL-2 in response to sonicated BCG or PPD derived from Mycobacterium tuberculosis but not to 65 kd heat shock protein (HSP) derived from M. bovis. These results suggest that gamma/delta T cells precede alpha/beta T cells in appearance during mycobacterial infection and the early appearing gamma/delta T cells may participate in the protection at the early stage against the mycobacterial infection.