Figure 2.

Assessment of T cell reactivity. PBMC of KTR (n=24) were stimulated or not with spike peptide mix. Specific CD4⁺ T cells were identified and quantified 7±2 days after the second and third vaccination by FACS according to CD137 and CD154 coexpression. Depicted are (A) the percentage of individuals with a cellular response (left, Fisher’s exact test), frequencies of specific CD4⁺ T cells (middle, paired Wilcoxon test), and frequencies within humoral responders (anti–S1 IgG⁺) and nonresponders (anti–S1 IgG^-) (right, unpaired t test). (B) Frequencies of antigen-specific CD4⁺ T cells expressing Ki67 (left, paired t test) or PD1 (right, paired t test). (C) Memory/effector subset differentiation of spike-reactive CD4⁺ T cells (T_CM, central memory, left, paired Wilcoxon test; T_EM, effector memory, middle, paired t test; T_eff, effector right, paired t test, T cells). (D) Expression of IFN-γ (paired t test), TNF-α (paired t test), IL-2 (paired Wilcoxon test), and IL-4 (paired Wilcoxon test in antigen-specific T cells including analysis of IFN-γ⁺TNF-α⁺IL-2⁺ “triple⁺” polyfunctional (paired Wilcoxon test) cells. Where applicable, graphs show mean±SD.