Biological functions of t cell lines with specificity for the intracellular bacterium Listeria monocytogenes in vitro and in vivo.

Peritoneal exudate T lymphocytes from mice immunized with live Listeria monocytogenes were cloned in double-layer soft agar containing heat-killed L. monocytogenes (lower layer) and syngeneic accessory cells (upper layer). Colony-derived T cells were propagated in vitro in the presence of listerial antigen, syngeneic accessory cells, and T cell growth factor. In vitro proliferation, interleukin secretion, and bystander help for B cells of six such T cell lines and several sublines derived from them were found to be antigen dependent and restricted by the H-2IA locus of the major histocompatibility complex. In vivo, these T cell lines conferred delayed-type hypersensitivity to listerial antigen and protection to live L. monocytogenes. It is concluded that different biological functions of acquired antibacterial immunity can be mediated by a single T cell population.