T lymphocyte dynamics during Listeria monocytogenes infection

Infection of mice with Listeria monocytogenes results in a robust T lymphoc yte response that clears the pathogen and provides long term immunity from reinfection. The number of splenic CD4(+) and CD8(+) T cells and natural ki ller cells increases during primary and recall infection with L. monocytoge nes, however the proportional increase is greatest for CD8(+) T cells. The proportion of CD8 T cells expressing low levels of CD62L, a sign of activat ion, was increased among immune splenocytes, suggesting a substantial expan sion of L. monocytogenes specific CTL. Analysis of CTL specific for the imm unodominant LLO 91-99 epitope showed that essentially all were CD62L(lo) du ring the primary response, but that many upregulated expression of CD62L du ring the memory phase. Interestingly, the antigen specificity of nearly all additional CD62L(lo) CTL detected in spleens during recall L. monocytogene s 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. (C) 1999 Elsevier Science B.V. All rights reserved.