title: T-cell activation, proliferation and apoptosis in primary Listeria monocytogenes infection.
abstract: Listeria monocytogenes infection of mice leads to a rapid expansion of activated T cells, followed by a decline in specific cells once the bacteria are eliminated. In order to define the relationship between T-cell proliferation and activation, and to investigate the role of apoptosis in limiting the expansion, the expression of activation markers, uptake of 5-bromo-2'-deoxyuridine (BrdU) in vivo and the incidence of apoptosis was investigated. Increased numbers of T cells expressing the activated phenotype CD25+, CD44hi and CD62Llo were detected 4 days after infection. Expression of CD25 (IL-2Ralpha chain) on CD4+ and CD8+ T cells peaked at this time and returned to normal by day 7. In contrast, CD44hi and CD62Llo persisted, with the maximum proportion occurring at 7 days after infection. This was accompanied by a burst of in vivo proliferation of CD4+ and CD8+ T cells occurring between day 5 and 7. Apoptosis, which is presumably needed to control this expansion of T cells, also peaked at 7 days after infection. Apoptosis occurred preferentially amongst T cells which had proliferated. Most but not all proliferating T cells had down-regulated their CD62L marker. While most apoptotic T cells were CD62Llo, again not all had down-regulated this marker. Hence, CD25 expression peaked early, but expression of other activation markers, in vivo proliferation and apoptosis coincided after Listeria infection. T cells that had proliferated were over-represented in the apoptotic population.
authors.affiliation: Department of Microbiology and Immunology, University of Melbourne, Victoria Australia.
authors.forename: Stuart I
authors.initials: SI
authors.lastname: Mannering
authors.forename: Jie
authors.initials: J
authors.lastname: Zhong
authors.forename: Christina
authors.initials: C
authors.lastname: Cheers
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D018960:Hyaluronan Receptors / Q000378:metabolism; D019041:L-Selectin / Q000378:metabolism; D008088:Listeriosis / Q000276:immunology*; D008213:Lymphocyte Activation; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D016176:T-Lymphocyte Subsets / Q000276:immunology*
chemical_list: D018960:Hyaluronan Receptors; D015375:Receptors, Interleukin-2; D019041:L-Selectin