Adapter protein which non-covalently associates with activating receptors found on the surface of a variety of immune cells to mediate signaling and cell activation following ligand binding by the receptors (By similarity). TYROBP is tyrosine-phosphorylated in the ITAM domain following ligand binding by the associated receptors which leads to activation of additional tyrosine kinases and subsequent cell activation (By similarity). Also has an inhibitory role in some cells (By similarity). Non-covalently associates with activating receptors of the CD300 family to mediate cell activation (By similarity). Also mediates cell activation through association with activating receptors of the CD200R family (By similarity). Required for neutrophil activation mediated by integrin (By similarity). Required for the activation of myeloid cells mediated by the CLEC5A/MDL1 receptor (By similarity). Associates with natural killer (NK) cell receptors such as the KLRD1/KLRC2 heterodimer to mediate NK cell activation (By similarity). Associates with TREM1 to mediate activation of neutrophils and monocytes (By similarity). Associates with TREM2 on monocyte-derived dendritic cells to mediate up-regulation of chemokine receptor CCR7 and dendritic cell maturation and survival (By similarity). Association with TREM2 mediates cytokine-induced formation of multinucleated giant cells which are formed by the fusion of macrophages (By similarity). Stabilizes the TREM2 C-terminal fragment (TREM2-CTF) produced by TREM2 ectodomain shedding which suppresses the release of pro-inflammatory cytokines (By similarity). In microglia, required with TREM2 for phagocytosis of apoptotic neurons (By similarity). Required with ITGAM/CD11B in microglia to control production of microglial superoxide ions which promote the neuronal apoptosis that occurs during brain development (By similarity). Promotes pro-inflammatory responses in microglia following nerve injury which accelerates degeneration of injured neurons (By similarity). Positively regulates the expression of the IRAK3/IRAK-M kinase and IL10 production by liver dendritic cells and inhibits their T cell allosimulatory ability (By similarity). Negatively regulates B cell proliferation (By similarity). Required for CSF1-mediated osteoclast cytoskeletal organization (By similarity). Positively regulates multinucleation during osteoclast development (By similarity). Homodimer; disulfide-linked (By similarity). Homotrimer; disulfide-linked (By similarity). Homotetramer; disulfide-linked (By similarity). Homotrimers and homotetramers form when low levels of partner receptors are available and is competitive with assembly with interacting receptors (By similarity). They may represent alternative oligomerization states or may be intermediates in the receptor assembly process (By similarity). Binding of a metal cation aids in homooligomerization through coordination of the metal ion by the subunits of the oligomer (By similarity). Interacts with TREM1 (By similarity). Interacts with TREM2 (By similarity). Interacts with CLECSF5 (By similarity). Interacts with CD300LB and CD300C2 (By similarity). Interacts with CD300E (By similarity). Interacts (via ITAM domain) with SYK (via SH2 domains); activates SYK mediating neutrophils and macrophages integrin-mediated activation (By similarity). Interacts with KLRC2 (By similarity). Interacts with CD300H (By similarity). Interacts with KLRD1 (By similarity). Following ligand binding by associated receptors, tyrosine phosphorylated in the ITAM domain which leads to activation of additional tyrosine kinases and subsequent cell activation. Belongs to the TYROBP family.