T lymphocyte dynamics during Listeria monocytogenes infection

Infection of mice with Listeria monocytogenes results in a robust T lymphocyte response that clears the pathogen and provides long term immunity from reinfection. The number of splenic CD4+ and CD8+ T cells and natural killer cells increases during primary and recall infection with L. monocytogenes, however the proportional increase is greatest for CD8+ T cells. The proportion of CD8 T cells expressing low levels of CD62L, a sign of activation, was increased among immune splenocytes, suggesting a substantial expansion of L. monocytogenes specific CTL. Analysis of CTL specific for the immunodominant LLO 91-99 epitope showed that essentially all were CD62Llo during the primary response, but that many upregulated expression of CD62L during the memory phase. Interestingly, the antigen specificity of nearly all additional CD62Llo CTL detected in spleens during recall L. monocytogenes infection can be accounted for with MHC class I tetramers complexed with four different epitopes. These studies demonstrate the complex T lymphocyte dynamics during infection with intracellular pathogens.