A knockout approach to understanding CD8+ cell effector mechanisms in adaptive immunity to Listeria monocytogenes.

In the described experimental approach, we use an attenuated LM strain to evoke LM specific CD8+ T cell responses. In this fashion, we can immunize immunocompromised gene knockout mice, that would succumb to low level infection with virulent LM. We then generate antigen matched, LM-specific CD8+ T cell lines from wild-type and gene knockout mice, and compare their capacity to provide immunity to LM infection in vivo. To date, our results demonstrate that CD8+ T cell-derived IFN-gamma and TNF are not required effector functions. Perforin deficiency has an impact on CD8+ T cell immunity but our studies provide strong evidence for the existence of perforin independent pathways of CD8+ T cell immunity to LM. To assess the potential for redundancy in effector mechanisms, we have generated mice deficient in both perforin and IFN-gamma and are developing mice deficient in perforin and TNF. By removing the major CD8+ T cell effector mechanisms, singly and in combination, we will eventually determine whether immunity to LM can be provided by redundant effector pathways or if novel effector mechanisms exist beyond our current knowledge. The generation of MHC matched, single and double knockout mice, will also aid in continuing studies to analyze the role of these molecules in resistance to in vivo infection.