The protein encoded by this gene belongs to the membrane-associated guanylate kinase (MAGUK) family, a class of proteins that functions as molecular scaffolds for the assembly of multiprotein complexes at specialized regions of the plasma membrane. This protein is also a member of the CARD protein family, which is defined by carrying a characteristic caspase-associated recruitment domain (CARD). CARD11 (CARMA1) has a domain structure similar to that of CARD10 (CARMA3) and CARD14 (CARMA2) as a member of the CARD-CC family with a C terminal MAGUK domain (the so-called CARMA proteins). The CARD domain of proteins in the CARD-CC family have been shown to specifically interact with BCL10, a protein known to function as a positive regulator of NF-κB activation by recruitment and activation of MALT1. When overexpressed in cells, this protein family activates NF-κB and induces the phosphorylation of BCL10. CARD11 is critical for T cell and B cell function and is activated after T cell receptor or B cell receptor stimulation. After receptor stimulation, CARD11 is phosphorylated by PKC-θ (in T cells) or PKC-β (in B cells). The phosphorylation induces formation of filamentous CARD11 multimers that recruit BCL10 and MALT1, which in turn activates NF-κB. Loss of function mutations in CARD11 cause severe combined immunodeficiency (SCID) since the function of cells critical for adaptive immunity are disrupted.