Characterization of peripheral T_FH cells.

<p>(<b>A</b>) Left: Representative flow cytometry plots from HIV-uninfected PBMC showing the gating scheme for isolating T cell subsets for the T cell/B cell coculture assay. Isolated populations include naïve cells (brown), CM CCR7^low (pink), CM CCR7^highCXCR5^low (orange), CM CCR7^highCXCR5^highCCR6^lowPD-1^high (green), CM CCR7^highCXCR5^highCCR6^highPD-1^low (blue) and CCR7^highCXCR5^highCCR6^highPD-1^high (red). Before gating on CCR6 and PD-1, cells were first gated on CD150^high. Right: Scatter plot indicating the frequency of each population in HIV-uninfected subjects (<i>n</i> = 13). Cells were not gated on CD150 for phenotypic analysis. (<b>B</b>) Indicated CD4 T cell populations were cultured with autologous naïve B cells (CD19^highCD27^lowIgD⁻) in the presence of SEB for 12 days and Ig concentrations were measured from supernatants (n = 6). (<b>C</b>) Indicated CD4 T cell populations were cultured with autologous naïve B cells in the presence of SEB for 2 days and cytokine concentrations were measured from supernatants (n = 6). Horizontal lines indicate limit of detection. Significant differences were determined using the Friedman test with Dunn's multiple comparison post-test. *p<0.05; **p<0.01.