Substantial in vivo proliferation of CD4(+) and CD8(+) T lymphocytes during secondary Listeria monocytogenes infection

In mice Listeria monocytogenes infection induces a strong T cell response. In an attempt to quantitatively analyze the magnitude and kinetics of the C D4(+) and CD8(+) T cell response during L. monocytogenes infection in vivo we used a T cell transfer system that is independent of in vitro cell cultu re techniques and information about the identity of immunogenic T cell epit opes. Our results demonstrate substantial expansion of the in vivo primed a nd transferred T cell populations in response to L, monocytogenes. At the p eak of response, transferred T cells represented more than one third of the total CD4(+) and CD8(+) T cell populations in blood and spleen of recipien t mice. After stimulation in vitro, 40 % of these CD4(+) T cells responded to heat-killed listeriae with the production of IFN-gamma. Thus, our result s reveal that in addition to the large CD8(+) T cell population an almost e qually large population of Listeria-reactive CD4(+) T cells is generated in response to L. monocytogenes infection.