A PROTECTIVE ROLE OF GAMMA-DELTA T-CELLS IN PRIMARY INFECTION WITH LISTERIA-MONOCYTOGENES IN MICE

We have previously reported that T cells bearing T cell receptors (TCRs) of gamma/delta-type appear at a relatively early stage of primary infection with Listeria monocytogenes in mice. To characterize the early-appearing gamma/delta-T cells during listeriosis, we analyzed the specificity and cytokine production of the gamma/delta-T cells in the peritoneal cavity in mice inoculated intraperitoneally with a sublethal dose of L. monocytogenes. The early-appearing gamma/delta-T cells, most of which were of CD4- CD8- phenotype, proliferated and secreted IFN-gamma and macrophage chemotactic factor in response to purified protein derivative from Mycobacterium tuberculosis, or recombinant 65-kD heat-shock protein derived from M. bovis but not to heat-killed Listeria. To further elucidate the potential role of the gamma/delta-T cells in the host-defense mechanism against primary infection with Listeria, we examined the effects of in vivo administration of monoclonal antibodies (mAbs) against TCR-gamma/delta or TCR-alpha/beta on the bacterial eradication in mice infected with Listeria. Most of alpha/beta-T cells or gamma/delta-T cells were depleted in the peripheral lymphoid organs at least for 12 d after an intraperitoneal injection of 200 gg TCR-alpha/beta-mAb or 200-mu-g TCR-gamma/delta-mAb, respectively. An exaggerated bacterial multiplication was evident at the early stage of listerial infection in the gamma/delta-T cells-depleted mice, whereas the alpha/beta-T cell-depleted mice exhibited much the same resistance level as the control mice at this stage although the resistance was severely impaired at the late stage after listerial infection. These results clearly indicated that the early-appearing gamma/delta-T cells contribute to the host defense at the early stage of infection with Listeria and confirmed previous reports that the highly evolved type of immunity mediated by Listeria-specific alpha/beta-T cells contributes to the host protection at the late stage after listerial infection.