In vivo anti-PD-L1 treatment prevents development of typical CLL-induced aberrant T-cell phenotype. Fresh cells of isotype (n = 10), aPD-L1-treated (n = 15), and hWT (n = 6) mice were stained for CD3, CD4, CD8, CD44, CCR7, and CD62L, and T cells were gated on DAPI-negative, viable, single MNCs. (A) CD3⁺ T cells from spleen, depicted as percentage of all lymphocytes, as well as CD4⁺ and CD8⁺ T cells, depicted as percentage of all CD3⁺ T cells, were compared. (B) CD4⁺:CD8⁺ ratios among CD3⁺ T cells were calculated for cells in spleen, PB, and BM and compared between isotype, aPD-L1, and hWT mice. (C) Naïve (CD44^–CD62L⁺), effector (Eff; CD44⁺CD62L^–), memory (Mem; CD44⁺CD62L⁺), effector memory (EM; CD44⁺CD62L^–CCR7^–), and central memory (CM; CD44⁺CD62L⁺CCR7⁺) T cells were quantified and are presented as percentage of CD3⁺CD8⁺ cells in spleen. (D) The percentages of antigen-experienced (Ag-exp.) CD44⁺CD3⁺CD8⁺ T cells expressing exhaustion markers PD-1, KLRG-1, 2B4, LAG3, and CD160 were quantified in spleen. (E) Naïve (CD44^–CD62L⁺), Ag-exp. CD44⁺, EM (CD44⁺CD62L^–CCR7^–), and CM (CD44⁺CD62L⁺CCR7⁺) CD3⁺CD4⁺ T cells and the percentage of Ag-exp. CD44⁺CD3⁺CD4⁺ T cells expressing PD-1 were quantified in spleen. All graphs depict mean ± SD. *P < .05; **P < .001; ***P < .0001.