Plasma levels of IL-21 correlate with frequency of HCV-specific CD8 T cells.

<p>(<b>A</b>) Increased plasma levels of IL-21 during acute resolving HCV. Plasma levels of the Th17 cytokines IL-17A and IL-21 were measured by ELISA at the indicated time points in SR (n = 8–12) and CI (n = 8–22) patients or healthy donors (HD) (n = 17). (<b>B</b>) Frequency of HCV-specific CD8 T cells correlates with plasma IL-21 levels. The frequency of HCV-specific CD8 T cells was measured using the following HLA class I tetramers (A1/NS3-1436, A2/NS3-1073, A2/NS3-1406, A2/NS5b-2594, B7/Core-41, B8/NS3-1395 and B27/NS5b-2841) and IL-21 levels were measured in paired plasma samples from 28 acute HCV patients. Correlation was tested using the Spearman correlation test.