Transfer to a lymphopenic host reveals dysregulated responses of MTS/ΔSLP CD4⁺ T cells independent of thymic development. (A) Diagram of selective induction of the MTS mutation followed by sorting and adoptive transfer into lymphopenic hosts. (B) Surface expression of activation markers after adoptive transfer of YFP⁺CD4⁺ +/ΔSLP (solid line) or MTS/ΔSLP (shaded) T cells. Histograms are gated on YFP⁺CD4⁺ T cells. Data are representative of 2 independent experiments using 3 mice per group. (C) After adoptive transfer, peripheral cells were stimulated with PMA plus ionomycin and stained for the presence of intracellular inflammatory cytokines. Populations are gated on YFP⁺ CD4⁺ T cells. Data are mean ± SEM and are representative of 3 independent experiments using 3 mice per group. (D) Staining for the intracellular incorporation of BrdU. Histograms are gated on YFP⁺CD4⁺ T cells. (E) Total number of recovered YFP⁺CD4⁺ T cells from RAG^−/− recipients. Data are mean ± SEM and are representative of 1 experiment using 3 mice per group. Significance was determined using the 2-tailed Student t test. *P < .05