Re-evaluation of the contribution of TNFRSF13B variants to antibody deficiency.

Predominantly antibody deficiency (PAD) is the most prevalent form of human inborn errors of immunity (IEI). PAD is characterized by recurrent bacterial infections, immune dysregulation, and impaired immunoglobulin production. A monogenic cause of PAD can be identified in about 20% of cases. Approximately 10% of patients carry heterozygous mutations in the tumor necrosis factor receptor superfamily member 13B gene (TNFRSF13B), encoding the B cell surface protein TACI. Heterozygous variants in TNFRSF13B are not sufficient to cause PAD, as approximately 1% of the healthy population carries one of these variants. To identify additional genetic contributors to the immune defect in these individuals, we examined the exomes of 161 PAD patients with rare-damaging variants in TNFRSF13B. We identified (i) biallelic mutations in TNFRSF13B, (ii) the HLA-class II marker (DPA1*03), and (iii) multiple single nucleotide polymorphisms in known B-cell related genes, as additional genetic risk factors. Moreover, pathogenic mutations in other known IEI genes were presented in 16% of patients with heterozygous TNFRSF13B variants.