Effect of DTA-mediated deletion of CD134+CD4+ T cells on CD8+ T cell homeostasis. (a) TNF-α and IFN-γ production and CD62L, CD43 and CD25 expression in gated memory CD44hiCD8+ T cells from Tnfrsf4Cre/+R26Dta/+ (DTA) and littermate control Tnfrsf4Cre/+ R26+/+ (WT) mice (n = 5-12). Cytokine production was assessed following 4-h in vitro stimulation of total spleen and lymph node cells. (b) CFSE dilution profiles of purified naïve (CD44lo) CD45.1+ CFSE-labeled wild-type CD8+ T cells 6 days following adoptive transfer into Tnfrsf4Cre/+ R26Dta/+ (DTA host), control Tnfrsf4Cre/+ R26+/+ (WT host) or lymphopenic Rag1-/- recipient mice (Rag1-/- host). Numbers within the plot represent the mean percentage of CFSE- donor CD8+ T cells in three mice per group. (c) Percentage of BrdU+ cells in memory CD44hiCD8+ T cells and (d) absolute number (mean ± SEM, n = 4) of BrdU+ cells in total CD8+ T cells following a 6-day period of BrdU administration. (e) CD44 and CD25 expression in gated CD8+ T cells of either DTA BM origin or B6 BM origin and (f) CD4:CD8 ratio (± SEM) in Rag1-/- recipients reconstituted with either DTA or CD45.1+ B6 bone marrow (single) or a 1:1 mixture of DTA and CD45.1+ B6 bone marrow (mixed) (n = 4-7).