The aggressive activated B cell-like subtype of diffuse large B-cell lymphoma is characterized by aberrant B-cell receptor (BCR) signaling and constitutive nuclear factor kappa-B (NF-kappaB) activation, which is required for tumor cell survival. BCR-induced NF-kappaB activation requires caspase recruitment domain-containing protein 11 (CARD11), and CARD11 gain-of-function mutations are recurrently detected in human diffuse large B-cell lymphoma (DLBCL). Enforced activation of CARD11/BCL1/MALT1 signaling is sufficient to drive transformed B-cell expansion in vivo and identify the JNK pathway as a therapeutic target for ABC-DLBCL. The scaffold protein caspase recruitment domain-containing protein 11 (CARD11) is implicated in the regulation of inflammation and autoimmunity. CARD11 is involved in the pathogenesis of CIA by formation of the CARD11/Bcl1 complex and enhancement of the Th17 cell response. Targeting CARD11 provides a novel research direction in the development of therapeutic strategies for RA. CARD11 is a multidomain adapter that is required for TCR signaling to the IkappaB kinase (IKK) complex. During TCR signaling, the region in CARD11 between the coiled-coil and PDZ domains is phosphorylated by protein kinase Ctheta (PKCtheta) in a required step in NF-kappaB activation. CARD protein 11 (CARD11) and CARD protein 14 (CARD14) are novel CARD-containing proteins that belong 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.