ANALYSIS OF THE ROLE OF NATURAL-KILLER-CELLS IN LISTERIA-MONOCYTOGENES INFECTION - RELATION BETWEEN NATURAL-KILLER-CELLS AND T-CELL RECEPTOR-GAMMA-DELTA T-CELLS IN THE HOST-DEFENSE MECHANISM AT THE EARLY-STAGEOF INFECTION

We have reported that T cells bearing T-cell receptors (TcR) of gamma delta type (gamma delta T cells) appear in the peritoneal cavity in a relatively early stage of primary intraperitoneal (i.p.) Listeria mono cytogenes infection, and play a significant role against the infection . To elucidate the protective role of natural killer cells which also appear in the early stage of L. monocytogenes infection, mice were tre ated with anti-NK1.1 monoclonal antibody (mAb) to deplete NK cells bef ore the infection. They exhibited accelerated clearance of L. monocyto genes, accompanied by enhanced induction of gamma delta T cells in the peritoneal cavity compared with non-treated mice. When the mice were depleted of gamma delta T cells by in vivo administration of anti-TcR gamma delta mAb, the bacterial burdens of organs from infected mice we re not affected by NK cell depletion. These results suggest that, alth ough NK cells increase significantly during the early stage oft. monoc ytogenes infection, they do not take part in the early host resistance against i.p. L. monocytogenes infection. It is also suggested that in creased gamma delta T cells in the peritoneal cavity of NK cell-deplet ed mice can be one of the factors responsible for the enhanced clearan ce of L. monocytogenes in the early stage of infection.