THE APPEARANCE AND ROLE OF GAMMA-DELTA T-CELLS IN THE PERITONEAL-CAVITY AND LIVER DURING PRIMARY INFECTION WITH LISTERIA-MONOCYTOGENES IN RATS

We have previously reported that gammadelta T cells play important roles in protection during the early stage of infection with Listeria monocytogenes in mice. To generalize the protective roles of gammadelta T cells in listerial infection to different species, we examined the appearance of gammadelta T cells during infection with L. monocytogenes in Fisher F344 rats. The numbers of bacteria in the peritoneal cavity and liver increased to a maximum level on day 3 and then decreased to an undetectable level by day 10 after an intraperitoneal infection with a sublethal dose (i x 108) of viable L. monocytogenes in rats. CD3+alphabeta- T cells in the peritoneal cavity and liver began to increase on day 3, reached a maximum level on day 6, and thereafter decreased gradually by day 10 after infection. Northern blot analysis confirmed that the CD3+alphabeta- T cells expressed TCR delta and gamma gene messages. In vivo treatment with anti-TCRalphabeta mAb, which suppressed most of the alphabeta T cells in the periphery and impaired resistance during the late stage of listerial infection, did not affect the host defense by day 6 after infection. A significantly increased number of gammadelta T cells was detected in the peritoneal cavity of the TCRalphabeta-suppressed rats on day 6 after infection. These results suggest that the early appearing gammadelta T cells may contribute to the host defense at a relatively early stage during listeriosis in rats.