Lipid tetraspanin-associated transmembrane adapter/mediator that acts as a scaffold for Src-family kinases and other signaling proteins in immune cells (PubMed:27288407, PubMed:28290451, PubMed:28098138). It is involved in major histocompatibility complex class II (MHC-II) signaling transduction in B cells, where it is required in generating the calcium response and enhancing ERK activity upon MHC-II stimulation (By similarity). In dendritic cells, it is involved in sustaining CLEC7A/DECTIN1 signaling after CLEC7A activation by fungal beta-glucans (PubMed:27288407). It also acts as an agonist-inducible signaling adapter for TLR1, TLR2, TLR3, TLR4, and TLR7 by selectively enabling the expression of pro-inflammatory cytokines IL6 and IL12B in macrophages and acting as a scaffold for phosphorylation of Toll-like receptors by Src-family kinases (PubMed:28098138). Interacts with CD37, CD53 and CD81 (By similarity). Interacts (via proline-rich region) with LYN (via SH3 domain) (PubMed:28098138). Interacts with CSK (via SH2 domain); this interaction is dependent on phosphorylation of Tyr-96 (PubMed:28290451). Interacts with BLNK (via SH2 domain); this interaction is dependent on phosphorylation of Tyr-120 (PubMed:21930792, PubMed:28290451). Interacts with GRB2 (via SH2 domain); this interaction may be dependent on phosphorylation of Tyr-58 (PubMed:21930792, PubMed:28098138). Interacts with TLR4; this interaction occurs upon lipopolysaccharide activation of TLR4 and is enhanced by phosphorylation of Tyr-96 by LYN (PubMed:28098138). This interaction facilitates the phosphorylation of TLR4 by LYN which elicits a selective cytokine response in macrophages (PubMed:28098138). Together with MHC-II, associates with lipid-enriched microdomains called tetraspanin-enriched microdomains (TEMs) (By similarity). Rapidly translocates into immunological synapse (IS) at cell-cell contacts between antigen-presenting cells (APCs) and T-cells (By similarity). Colocalized with tetraspanins CD37, CD53, and CD81 at the uropod (By similarity). Present at regions of cell-cell contacts but also at the leading edge of migrating cells (By similarity). Localizes to phagosomes in dendritic cells after exposure to particulate beta-glucan (PubMed:27288407). Expressed in peripheral blood leukocytes (PBLs) (at protein level) (PubMed:21930792). Expressed in dendritic cells, splenocytes and B cells (at protein level) (PubMed:27288407). Strongly expressed in the spleen and lymph nodes and weakly in other tissues of the immune system, including bone marrow, peripheral blood leukocytes (PBLs) and thymus (PubMed:21930792). Not detected in the majority of nonimmune tissues, with the exception of lung (PubMed:21930792). Expressed in antigen-presenting cells (PubMed:21930792). Expressed in macrophages (PubMed:28098138). Induced in bone marrow-derived macrophages by CSF2 and particulate beta-glucan. Phosphorylated by the Src-family protein tyrosine kinases LYN and SRC (PubMed:27288407). Phosphorylation occurs on tyrosine residues upon MHC-II stimulation (PubMed:21930792, PubMed:27288407). Phosphorylation also occurs on tyrosine residues after activation of CLEC7A/DECTIN1 by particulate beta-glucan (PubMed:27288407). Lipopolysaccharide (LPS) induces phosphorylation of Tyr-58, Tyr-96 and Tyr-120 differentially to allow temporal recruitment of effector proteins GRB2, CSK and BLNK (PubMed:28290451). Phosphorylation of Tyr-58 is immediately induced by LPS stimulation and allows GRB2 to bind (PubMed:28290451). Tyr-96 is phosphorylated 5 minutes after LPS stimulation, which then allows CSK to bind, followed by phosphorylation of Tyr-120 10 minutes after LPS induction, which allows BLNK to bind (PubMed:28290451). Phosphorylation at Tyr-96 by LYN occurs after activation of TLR4 by LPS; phosphorylation enhances binding to TLR4 (PubMed:28098138, PubMed:28290451). Palmitoylated. Mice exhibit no difference in leukocyte development and subset representation in lymphoid organs (PubMed:27288407). No effect on B cell mediated activation of antigen-specific T cells and MHCII glycoprotein downstream signaling in B cells (PubMed:27288407). In dendritic cells, mutants show decreased cytokine production beyond 24 hours after stimulation of CLEC7A signaling (PubMed:27288407). Truncated N-terminus. Truncated N-terminus.