SEMA4C and common variable immunodeficiency: While we are in the process of evaluating memory and antigen responses in the murine system, we present intriguing preliminary data in individuals with CVID, specifically those with very low memory B-cells and associated poor antibody production, who have impaired upregulation of Sema4C mRNA and impaired synapse formation, analgous to Sema4C−/− mice.