The receptor repertoire and functional profile of follicular T cells in HIV-infected lymph nodes.

Follicular helper CD4+ T cells (TFH ) play an integral role in promoting B cell differentiation and affinity maturation. Whereas TFH cell frequencies are increased in lymph nodes (LNs) from individuals infected with HIV, humoral immunity remains impaired during chronic HIV infection. Whether HIV inhibits TFH responses in LNs remains unclear. Advances in this area have been limited by the difficulty of accessing human lymphoid tissues. Here, we combined high-dimensional mass cytometry with T cell receptor repertoire sequencing to interrogate the composition of TFH cells in primary human LNs. We found evidence for intact antigen-driven clonal expansion of TFH cells and selective utilization of specific complementarity-determining region 3 (CDR3) motifs during chronic HIV infection, but the resulting TFH cells acquired an activation-related TFH cell signature characterized by interleukin-21 (IL-21) dominance. These IL-21+ TFH cells contained an oligoclonal HIV-reactive population that preferentially accumulated in patients with severe HIV infection and was associated with aberrant B cell distribution in the same LN. These data indicate that TFH cells remain capable of responding to HIV antigens during chronic HIV infection but become functionally skewed and oligoclonally restricted under persistent antigen stimulation.