Figure 6. Functional inhibition of CD8⁺ T cells depending on BTLA expression and HVEM triggering.

(A) Direct ex vivo analysis of percentage of A2/Melan-A^MART-1 tetramer⁺ CD8⁺ T cells among PBMCs, in relation to their BTLA expression, after vaccination without and with CpG. (B) In vitro expansion of Melan-A^MART-1 tetramer⁺ T cells from healthy donors, after 10 days of stimulation with peptide-loaded DCs, in the absence versus presence of blocking mAb BTLA-8.2. (C and D) IFN-γ (C) and TNF-α (D) production by BTLA⁺ antigen-specific CD8⁺ T cells after 4 hours of peptide stimulation of PBMCs assessed ex vivo, i.e., without prior in vitro cultivation. Representative histograms of PBMCs from patient LAU 618 (after 2 vaccinations, with CpG) and from healthy donor BCB122 stimulated by SKMEL37 cells expressing HVEM or not, loaded with Melan-A^MART-1 or EBV peptides, respectively. Histograms are gated on tetramer⁺ T cells. Percentages of cytokine-positive cells are indicated. (E) Significant correlation between percentages of BTLA⁺ tetramer⁺ T cells and percentages of IFN-γ production inhibition (i.e., reduction when stimulated with HVEM⁺ SKMEL37 cells as compared with HVEM^– SKMEL37 cells). Each dot represents a single experiment with Melan-A^MART-1– or EBV-specific T cells.