SLAM family member 9
cell surface
Signalling lymphocyte activation molecule family member 9 is found on select subsets of antigen-presenting cells and promotes resistance to Salmonella infection.
Signalling lymphocyte activation molecule family member 9 (SLAMF9) is an orphan receptor of the CD2/SLAM family of leucocyte surface proteins. Examination of SLAMF9 expression and function indicates that SLAMF9 promotes inflammation by specialized subsets of antigen-presenting cells. Within healthy liver and circulating mouse peripheral blood mononuclear cells, SLAMF9 is expressed on CD11b<sup>+</sup> , Ly6C<sup>-</sup> , CD11c<sup>low</sup> , F4/80<sup>low</sup> , MHC-II<sup>+</sup> , CX<sub>3</sub> CR1<sup>+</sup> mononuclear phagocytes as well as plasmacytoid dendritic cells. In addition, SLAMF9 can be found on peritoneal B1 cells and small (F4/80<sup>low</sup> ), but not large (F4/80<sup>high</sup> ), peritoneal macrophages. Upon systemic challenge with Salmonella enterica Typhimurium, Slamf9<sup>-/-</sup> mice were impaired in their ability to clear the infection from the liver. In humans, SLAMF9 is up-regulated upon differentiation of monocytes into macrophages, and lipopolysaccharide stimulation of PMA-differentiated, SLAMF9 knockdown THP-1 cells showed an essential role of SLAMF9 in production of granulocyte-macrophage colony-stimulating factor, tumour necrosis factor-α, and interleukin-1β. Taken together, these data implicate SLAMF9 in the initiation of inflammation and clearance of bacterial infection.