IL-12Rβ1 Deficiency Corresponding to Concurrency of Two Diseases, Mendelian Susceptibility to Mycobacterial Disease and Crohn's Disease.

Abstract Background The interleukin-12 receptor β1 (IL-12Rβ1) deficiency is a primary immunodeficiency (PID), affecting the immunological pathway of interleukin 12/interferon- γ (IL12/IFN-γ) axis and interleukin 23 receptor (IL23R). Defect in this pathway is mainly affecting the cellular immunity-related disorders. IL-12Rβ1 is a receptor chain of both the IL-12 and the IL-23 receptors and thus, deficiency of IL-12Rβ1 abolishes both IL-12 and IL-23 signaling. Material and methods In this study, we performed whole exon sequencing and confirmatory Sanger sequencing in IL-12Rβ1. Evaluation of the IL12/IFN-γ axis was performed by assessment of patients’ whole blood cell to IL12/IFN-γ responding. Total and surface IL-12Rβ1expression was evaluated, in peripheral blood mononuclear cells (PBMCs) and T cell- derived PBMCs, and Th17 count was assessed. Results In the present study, we described a c.1791+2T>G mutation at a splicing site position in IL-12Rβ1, using whole exome sequencing, and confirmed with targeted Sanger sequencing in a 26- year-old patient with Mendelian susceptibility to mycobacterial disease (MSMD) and Crohn's disease (CD). Complete lack of IL-12Rβ1 protein expression was detected in patient's PBMCs, compared to the healthy control. Furthermore, no IL-12Rβ1 protein was expressed on the cell surface. Interestingly, IL-12Rβ1-mutant cells showed an impaired response to IL12, and Bacillus Calmette–Guerin stimulation, confirming that the mutation is causative in this patient. Conclusion A 3’splicing site mutation in IL12Rβ1, can be corresponding to the abolished expression of IL12Rβ1 in patients' cells, and associated with an impaired IL12-mediated signaling, which may lead not only to MSMD, but also to inflammatory bowel disease (IBD).