Figure 1.

STAT3-deficient CD8⁺ T cells exhibit a preactivated phenotype. (a) Purified CD4⁺ or CD8⁺ T cells derived from the spleen and LN of control (STAT3^f/f) and CD4-STAT3KO mice (CRE^CD4STAT3^f/f) were analyzed by western blotting. (b) Eight-week-old WT or STAT3KO mice were euthanized, and lymph nodes (LN) and spleen were harvested. Total CD4⁺ and CD8⁺ lymphocytes isolated from LN and spleen were quantified on a Vi-CELL Cell Viability Analyzer (Beckman Coulter). (c) Freshly isolated T cells from the PBMC, LN, or spleen were stained with Abs to CD3, CD4, or CD8 and analyzed by FACS. (d, e, f) Relative amounts of activated T cells in unstimulated thymocytes (d, e) or spleen (f) of the WT or STAT3KO mice were determined by FACS analysis of CD44⁺ or CD62L⁺ T cells. Plots (d, e, f) were gated on CD3, and numbers in quadrants represent percentage of T cells expressing CD4, CD8, or CD44. Data represent at least 3 independent experiments.