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
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