Complement C1s subcomponent is a ~76 kDa protein. Component of the complement C1 complex, a multiprotein complex that initiates the classical pathway of the complement system, a cascade of proteins that leads to phagocytosis and breakdown of pathogens and signaling that strengthens the adaptive immune system. C1S is activated following association of the C1 complex with immunoglobulins (IgG or IgM) complexed with antigens to form antigen-antibody complexes on the surface of pathogens. C1S is cleaved and activated by C1R to generate C1s subcomponent heavy and light chains. C1s subcomponent light chain then cleaves and activates C2 and C4, the next components of the classical complement pathway. 1. Lacroix, M. et al. (2001) The Journal of biological chemistry 276, 36233-40. PMID: 114455892. Kerr, FK. et al. (2005) The Journal of biological chemistry 280, 39510-4. PMID: 161698533. Kerr, MA. et al. (1978) The Biochemical journal 171, 99-107. PMID: 4177284. Reboul, A. et al. (1979) FEBS letters 103, 156-61. PMID: 4676435. McRae, BJ. et al. (1981) The Journal of biological chemistry 256, 12362-6. PMID: 62717846. Thielens, NM. et al. (1982) FEBS letters 141, 19-24. PMID: 62826467. Thielens, NM. et al. (1984) FEBS letters 165, 111-6. PMID: 63191798. Nagasawa, S. et al. (1977) Proceedings of the National Academy of Sciences of the United States of America 74, 2998-3001. PMID: 707879. Rossi, V. et al. (1998) The Journal of biological chemistry 273, 1232-9. PMID: 942279110. Zwarthoff, SA. et al. (2021) Proceedings of the National Academy of Sciences of the United States of America 118. PMID: 34155115 | 
