Phenotype of human CD40L⁺ CD8⁺ T cells. (A) The left dot-plot shows representative gates for ex vivo–sorted CD3⁺ CD8⁺ CD4⁻ T-cell subsets based on CCR7 and CD45RA expression (CCR7⁺ CD45RA⁺ naive, CCR7⁺ CD45RA⁻ central memory, CCR7^- CD45RA⁻ effector memory, or CCR7⁻ CD45RA⁺ effector cells). The isolated cells were stimulated with P/I in the presence of αCD40 antibodies and were subsequently assessed for CD40L expression among activated CD69⁺ cells. (B) The frequencies of CD40L⁺ CD8⁺ T-cell subsets are shown as the median ± standard error of the mean (SEM) (n = 13); the Friedman test and Dunn’s post hoc test were used (***P < .001). (C) P/I-stimulated CD8⁺ T cells were analyzed for their capacity to coexpress CD40L with CD27, CD28, CD127, or CD57. (D) Ex vivo–sorted human memory CD8⁺CD45RA⁻ T cells were stimulated with P/I and subsequently separated into CD40L⁺ and CD40L⁻ fractions. Proliferation after 7 days in vitro culture with and without IL-2 and IL-12 was assessed by CFSE dilution and capability to re-express CD40L after 6-hour P/I stimulation. (C-D) One representative experiment out of 3 to 5 is shown.