Exposure to bacterial respiratory pathogens is commonplace, but severe recurrent disease requiring hospitalization may suggest an underlying IEI. We studied a pair of siblings with decade-long histories of severe recurrent lower respiratory tract infections and positive cultures for Streptococcus pnuemoniae. These patients had normal total B cell counts but reduced generation of B cell memory and low antibody levels. CyTOF analysis showed all other immune cell subsets were present at normal frequencies. No mutations in known IEI-causal genes explained these patients’ phenotypes. By whole-exome sequencing, we identified a novel mutation in TANK, which segregated in an autosomal recessive manner. This mutation caused a frameshift and early truncation of the TANK protein, and complete TANK deficiency in the patients’ cells. TANK is an adaptor protein with poorly characterized roles in both canonical and noncanonical NF-kB signaling. Using an in vitro B cell differentiation assay, we know that TANK-deficient patients’ B cells seem “blocked” at the IgD-CD27- double-negative stage and proliferate poorly. Using scRNA-seq of patient and healthy control samples, we show an accumulation of intermediate B cells with a unique gene, including high SOX5 expression. Mechanistically, TANK suppresses the canonical NF-kB pathway and serves as a critical determinant of B cell proliferation and differentiation, antibody secretion, and protection from respiratory pathogens.
