Sequential appearance of γ/δ- and α/β-bearing T cells in the peritoneal cavity during an i.p. infection with Listeria monocytogenes

To search for a potential role of T cell antigen receptor (TcR) γ/β-bearing cells in host-defense against Listeria monocytogenes, we analyzed the sequential appearance of γ/δ and α/β T cell in the peritoneal exudate cells (PEC) during an i.p. infection with sublethal dose (2 × 10³) of viable Listeria organisms in mice. The PEC on day 1 after the infection consisted of 48% macrophages and 50% lymphocytes, most of which were surface IgM⁺ (B) cells. The number of PEC increased to the maximal level by day 3. The PEC at this stage contained an appreciable number of CD3⁺ T cells in addition to a large number of macrophages. Of the CD3⁺ cells, the proportion of CD4^?CD8^? cells, most of which expressed no TcR α/β, increased to the maximal level on day 3 after the infection. In correlation with an increased number of CD3⁺CD4^?CD8^?TcR α/β^? cells, high level of TcR γ/δ chain gene messages was detected in the nonadherent population of the PEC on this stage. On the other hand, the PEC on day 8 contained an increased number of CD4⁺CD8^? and CD4^?CD8⁺ cells which expressed TcR α/β chain on their surface. These results suggest that the γ/δ T cells precede the α/β T cells in appearance during listerial infection. The γ/β T cells may be involved at the first line of the host-defense against Listeria.