Increased CD4⁺ T cell proliferation to EBNA1, but not HCMV-pp65 or influenza, in MS. PBMCs from 24 MS patients and 24 healthy virus carriers were stimulated with overlapping peptide libraries spanning the C-terminal domain of EBNA1 (aa 400–641), with the entire sequence of the HCMV-encoded pp65 protein (aa 1–561), and by influenza A virus infection. Antigen-specific proliferative responses were determined in a flow cytometry–based CFSE-dilution assay. (A) An analysis of a representative blood donor. (B) Summary of all positive responses. *, P = 0.004. Bars represent means.