Autocrine IL-2 production drives divergent responses in CD4 ⁺ and CD8 ⁺ T cells. Chimeric mice were generated using BM from WT (CD45.1⁺) and CD4^creRosa^IL-2 (CD45.2⁺) at varying ratios. n = 4–6, pooled from two independent experiments. (A) Total T cell numbers in spleen. (B) Correlation between indicated cell types. (C) Frequency of thymocyte subsets derived from CD4^creRosa^IL-2 (CD45.2⁺) after reconstitution. DP, double-positive; SP, single-positive. (D) Total number of naive (CD44^loCD62L^hi), Teff (CD44^hiCD62L^lo), or Tcm (CD44^hi CD62L^hi) cells in the spleen. (E) Comparison of splenocyte frequencies from experimental chimeras (50% WT, 50% CD4^creRosa^IL-2) with control chimeras (50% WT, 50% CD4^creRosa^wt) generated simultaneously. (F) tSNE representation of high-parameter flow cytometry data from splenic CD4⁺ (top) and CD8⁺ (bottom) T cells from 50% WT:50% CD4^creRosa^IL-2 chimeras. FlowSOM clusters annotated based on differential expression of key markers. D value represents cross-entropy distance between samples. (G) Heatmap showing differential marker expression in annotated FlowSOM clusters for CD4⁺ T cells (left) or CD8⁺ T cells (right).