The impact of NF-κB2 mutations on Tfh cell differentiation and their critical role in immune function.

Background: The non-canonical NF-κB2 pathway is crucial for immune regulation, and pathogenic mutations in NF-κB2 are linked to common variable immunodeficiency (CVID), recurrent infections, and autoimmune diseases. T follicular helper (Tfh) cells play a key role in B cell differentiation and antibody production, but the effects of NF-κB2 mutations on Tfh cell differentiation remain unclear. This study investigates the clinical and functional consequences of two NF-κB2 mutations: c.1714G>A (p.A572T) and c.2540dupT (p.R848Efs*38).

Methods: We analyzed clinical features, immunophenotypes, and endocrine profiles of three patients carrying NF-κB2 mutations. Transcriptome sequencing of peripheral blood mononuclear cells (PBMCs) from Patient 3 (P3) and five healthy donors was performed to examine gene expression changes. Flow cytometry quantified Tfh cell populations, and real-time quantitative polymerase chain reaction (RT-qPCR) validated the expression of genes involved in Tfh differentiation. The impact of NF-κB2 mutations on p100 processing and nuclear translocation was assessed via western blot and immunofluorescence in HEK293T cells.

Results: Patient 1 (P1) exhibited mild clinical features, primarily asthma, while Patient 3 (P3) presented with severe immunodeficiency, recurrent pulmonary infections, and hormonal deficiencies. Transcriptome sequencing revealed significant downregulation of T cell differentiation pathways in P3, particularly Tfh-related genes such as ASCL2, IRF4, and BHLHE40. Flow cytometry confirmed a marked reduction in circulating Tfh cells in P3. Western blot and immunofluorescence analyses demonstrated that the R848Efs*38 mutation impaired the conversion of p100 into p52 and disrupted nuclear translocation.

Conclusions: This study identifies novel mechanisms by which NF-κB2 mutations impair immune function. The R848Efs*38 mutation disrupts Tfh cell differentiation by interfering with p100 processing and reducing key Tfh-related transcription factors. These findings enhance our understanding of NF-κB2-related immunodeficiencies and their molecular underpinnings, contributing to the broader knowledge of immune regulation and potential therapeutic targets.