Expansion of a distinct cytotoxic CD4 T_FH-cell cluster in lymph nodes of patients with complicated common variable immunodeficiency.

Abstract

Patients with common variable immunodeficiency (CVID) suffer from hypogammaglobulinemia linked to an inadequate differentiation of long-lived humoral immunity and an impaired germinal center (GC) response in most cases. We sought to further characterize the transcriptome and phenotype of T follicular helper (T_FH) cells of patients with complicated CVID (CVIDc) as key players in the GC reaction. Sorted T_FH cells from CVIDc lymph nodes and non-CVID immunocompetent tonsils were analyzed by bulk RNA sequencing. Altered protein expression was verified by comparison with non-CVID tonsils and lymph nodes using cytometry by time-of-flight analysis. Tissue localization of cells was determined by multifluorescence imaging. Transcriptome analysis of sorted T_FH cells revealed an enrichment of cytotoxicity-associated gene sets in patients with CVIDc. Extended immune phenotyping identified different cytotoxic CD4 memory populations expressing T-bet, EOMES (eomesodermin), class I-restricted T-cell-associated molecule, perforin, and granzymes. One cluster coexpressing markers of T_FH differentiation C-X-C chemokine receptor type 5, inducible costimulator, and programmed cell death protein 1 was expanded in CVIDc lymph nodes. Histologic sections confirmed the increase in Granzyme-B⁺EOMES⁺CD4 cells within GCs of patients' lymph nodes. Only few of these cells circulate in peripheral blood. Our study reports for the first time that the type 1 polarization in lymph nodes of patients with CVIDc is associated with an expansion of a distinct cytotoxic CD4 T_FH-cell cluster within GCs, which is only poorly reflected in peripheral blood. Because a detrimental role of these cells has been implied in the context of autoimmunity and chronic infection, further investigations are required to explore their role in the GC failure and immune dysregulation in patients with CVID.