Specific targeting of memory and regulatory CD4+ T cells by Tnfrsf4-driven Cre expression. (a) Activated YFP expression in a subset of splenic (SP) and lymph node cells (LN) isolated from Tnfrsf4Cre/+ R26Yfp/+ mice. Numbers within dot plots denote the percentage of YFP+ cells. (b) Percentage (mean ± SEM, n = 6-9) of CD4+, CD8+ or CD19+ cells or cells negative for all three markers (other) in gated YFP+ cells from the spleen and lymph nodes of Tnfrsf4Cre/+R26Yfp/+ mice. (c, d) Percentage (mean ± SEM, n = 6-9) of YFP+ cells in (c) total, naïve (CD44loCD25-), memory (CD44hiCD25-) and regulatory (reg; CD25+) CD4+ T cells and in (d) total, naïve (CD44loCD25-) and memory (CD44hiCD25-) CD8+ T cells, both from the spleen and lymph nodes of Tnfrsf4Cre/+R26Yfp/+ mice. (e) Percentage (mean ± SEM, n = 4-8) of YFP+ cells in naïve, memory and regulatory CD4+ T cells from Tnfrsf4Cre/+ R26Yfp/+ (YFP/+) and Tnfrsf4Cre/+ R26Yfp/Dta(YFP/DTA) mice. (f) Flow cytometric example of YFP and CD134 induction 1 day (d1) after in vitro stimulation of sorted naïve YFP- CD4+ T cells (d0) from Tnfrsf4Cre/+ R26Yfp/+ mice. (g) Percentage of YFP+ and CD134+ cells (mean ± SEM, n = 4-6) in CD4+ T cells stimulated as in (f). (h) Percentage of annexin V+ cells following in vitro activation of sorted naïve CD4+ T cells from Tnfrsf4Cre/+R26Dta/+ (DTA) or control Tnfrsf4Cre/+R26+/+ (WT) mice.