Fig. 2.

Mutation in the NS3₁₃₇₆ epitope stimulates impaired activation and proliferation in a cognate CD4 T cell clone. (A) Activation of the NS3₁₃₇₆-specific CD4 T cell clone 3D was assessed by intracellular staining for the phosphorylated form of the mitogen-activated protein kinase ERK 1/2 following a 15-minute stimulation with various concentrations of the NS3₁₃₇₆ WT or NS3₁₃₇₆ M1 peptides. Representative histograms are shown. White histograms show phosphorylated ERK 1/2 staining levels in unstimulated control cells; levels in stimulated test cells are depicted by gray histograms. (B) CFSE-labeled CD4 T cell clone 3D cells were stimulated with either the NS3₁₃₇₆ WT or NS3₁₃₇₆ M1 peptides (0.01 μg/mL) and proliferation, measured as CFSE dilution by way of flow cytometric analysis, was determined on day 3, 4, or 5. Representative plots show gated live CD3⁺CD4⁺ cells with frequencies of cells that either remained undivided (CFSE^hi) or had undergone up to four rounds of division as indicated above each plot.