Adapter protein that plays a key role in adaptive immune response by transducing the activation of NF-kappa-B downstream of T-cell receptor (TCR) and B-cell receptor (BCR) engagement (PubMed:11278692, PubMed:11356195, PubMed:12356734). Transduces signals downstream TCR or BCR activation via the formation of a multiprotein complex together with BCL10 and MALT1 that induces NF-kappa-B and MAP kinase p38 (MAPK11, MAPK12, MAPK13 and/or MAPK14) pathways (PubMed:11356195). Upon activation in response to TCR or BCR triggering, CARD11 homooligomerizes to form a nucleating helical template that recruits BCL10 via CARD-CARD interaction, thereby promoting polymerization of BCL10 and subsequent recruitment of MALT1: this leads to I-kappa-B kinase (IKK) phosphorylation and degradation, and release of NF-kappa-B proteins for nuclear translocation (PubMed:24074955). Its binding to DPP4 induces T-cell proliferation and NF-kappa-B activation in a T-cell receptor/CD3-dependent manner (PubMed:17287217). Promotes linear ubiquitination of BCL10 by promoting the targeting of BCL10 to RNF31/HOIP (PubMed:27777308). Stimulates the phosphorylation of BCL10 (PubMed:11356195). Also activates the TORC1 signaling pathway (PubMed:28628108). Maintained in an autoinhibited state via homodimerization in which the CARD domain forms an extensive interaction with the adjacent linker and coiled-coil regions (PubMed:31296852). Activation downstream of T-cell receptor (TCR) by phosphorylation by PRKCB and PRKCQ triggers CARD11 homooligomerization and BCL10 recruitment, followed by activation of NF-kappa-B (By similarity). Homodimer; disulfide-linked (PubMed:24224005). Homomultimer; polymerizes following activation, forming a nucleating helical template that seeds BCL10-filament formation via a CARD-CARD interaction (PubMed:24074955). Interacts (via CARD domain) with BCL10 (via CARD domain); interaction takes place following CARD11 activation and polymerization, leading to the formation of a filamentous CBM complex assembly (PubMed:11278692, PubMed:11356195, PubMed:27777308, PubMed:24074955, PubMed:31296852). Component of a CBM complex (CARD11-BCL10-MALT1) complex involved in NF-kappa-B activation (PubMed:28628108, PubMed:24074955). Found in a membrane raft complex, at least composed of BCL10, CARD11, DPP4 and IKBKB (PubMed:17287217). Interacts (via PDZ domain) with DPP4 (via cytoplasmic tail) (PubMed:17287217). Colocalized with DPP4 in membrane rafts. Detected in adult peripheral blood leukocytes, thymus, spleen and liver. Also found in promyelocytic leukemia HL-60 cells, chronic myelogenous leukemia K-562 cells, Burkitt's lymphoma Raji cells and colorectal adenocarcinoma SW480 cells. Not detected in HeLaS3, MOLT-4, A-549 and G431 cells. The linker region, also named autoinhibitory interface, is less inhibitory on its own than that of CARD9 (PubMed:31296852). The linker region together with the inhibitory domain (ID) are required to prevent constitutive activation and maintain CARD11 in an autoinhibitory state (PubMed:31296852). Disruption of the inhibitory domain (ID) region triggers polymerization and activation, leading to formation of BCL10-nucleating filaments (PubMed:31296852). Phosphorylation at Ser-559, Ser-644 and Ser-652 by PRKCB and PRKCQ leads to a shift from an inactive to an active form that activates the NF-kappa-B signaling. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry.