STAT (signal transducers and activators of transcription) A family of seven transcription factors activated by many cytokine and growth factor receptors.
STAT3 See STAT.
STAT6 See STAT.
statins Drug inhibitors of HMG-CoA reductase used to lower cholesterol.
sterile injury   Damage to tissues due to trauma, ischemia, metabolic stress, or autoimmunity, bearing many immune features similar to infection.
sterilizing immunity An immune response that completely eliminates a pathogen.
STIM1 A transmembrane protein that acts as a Ca2+ sensor in the endoplasmic reticulum. When Ca2+ is depleted from the endoplasmic reticulum, STIM1 is activated and induces opening of plasma membrane CRAC channels.
STING (stimulator of interferon genes) A dimeric protein complex in the cytoplasm anchored to the ER membrane that functions in intracellular sensing for infection. It is activated by specific cyclic di-nucleotides to activate TBK1, which phosphorylates IRF3 to induce transcription of type I interferon genes.
stress-induced self See dysregulated self.
stromal cells The nonlymphoid cells in central and peripheral lymphoid organs that provide soluble and cell-bound signals required for lymphocyte development, survival, and migration.
subcapsular sinus (SCS) The site of lymphatic entry in lymph nodes lined by phagocytes, including subcapsular macrophages which capture particulate and opsonized antigens draining in from tissues.
sulfated sialyl-LewisX A sulfated tetrasaccharide carbohydrate structure attached to many cell surface proteins, it binds the P-selectin and E-selectin molecules on the surface of cells, such as neutrophils, that mediate interactions with the endothelium.
superoxide dismutase (SOD) An enzyme that converts the superoxide ion produced in the phagolysosome into hydrogen peroxide, a substrate for further reactive antimicrobial metabolites.
suppressor of cytokine signaling (SOCS)   Regulatory protein that interacts with JAK kinases to inhibit signaling by activated receptors.
supramolecular activation complex (SMAC) Organized structure that forms at the point of contact between a T cell and its target cell, in which the ligand-bound antigen receptors are co-localized with other cell-surface signaling and adhesion molecules. Also known as supramolecular adhesion complex.
surface immunoglobulin (sIg) The membrane-bound immunoglobulin that acts as the antigen receptor on B cells.
surfactant proteins A and D (SP-A and SP-D) Acute-phase proteins that help protect the epithelial surfaces of the lung against infection.
surrogate light chain A protein in pre-B cells, made up of two subunits, VpreB and λ5, that can pair with a full-length immunoglobulin heavy chain and the Igα and Igβ signaling subunits and signals for pre-B-cell differentiation.
switch regions   Genomic regions, several kilobases in length each, located between the JH region and the heavy-chain Cμ genes, or in equivalent positions upstream of other C-region genes (except Cδ), containing hundreds of G-rich repeated sequences that function in class switch recombination.
Syk A cytoplasmic tyrosine kinase found in B cells that acts in the signaling pathway from the B-cell antigen receptor.
symbiotic   Relationship between two agents, typically diverse species, that confers benefits to both.
sympathetic ophthalmia Autoimmune response that occurs in the other eye after one eye is damaged.
syngeneic graft A graft between two genetically identical individuals. It is accepted as self.
systemic immune system Name sometimes given to the lymph nodes and spleen to distinguish them from the mucosal immune system.