Mannose-binding protein A; Calcium-dependent lectin. Plays a role in the innate immune response by binding mannose, fucose and N-acetylglucosamine moieties on different microorganisms and mediating activation of the lectin complement pathway (By similarity). Binds to late apoptotic cells, as well as to apoptotic blebs and to necrotic cells, but not to early apoptotic cells, facilitating their uptake by macrophages (By similarity).

Plasma protease C1 inhibitor; Activation of the C1 complex is under control of the C1- inhibitor. It forms a proteolytically inactive stoichiometric complex with the C1r or C1s proteases. May play a potentially crucial role in regulating important physiological pathways including complement activation, blood coagulation, fibrinolysis and the generation of kinins. Very efficient inhibitor of FXIIa. May inhibit chymotrypsin and kallikrein.

Complement C4 alpha chain; Non-enzymatic component of C3 and C5 convertases and thus essential for the propagation of the classical complement pathway. Covalently binds to immunoglobulins and immune complexes and enhances the solubilization of immune aggregates and the clearance of IC through CR1 on erythrocytes. Catalyzes the transacylation of the thioester carbonyl group to form ester bonds with carbohydrate antigens (By similarity).

Mannan-binding lectin serine protease 1 heavy chain; Functions in the lectin pathway of complement, which performs a key role in innate immunity by recognizing pathogens through patterns of sugar moieties and neutralizing them. The lectin pathway is triggered upon binding of mannan-binding lectin (MBL) and ficolins to sugar moieties which leads to activation of the associated proteases MASP1 and MASP2. Functions as an endopeptidase and may activate MASP2 or C2 or directly activate C3 the key component of complement reaction. Isoform 2 may have an inhibitory effect on the activation of [...]

Ficolin-1; Extracellular lectin functioning as a pattern-recognition receptor in innate immunity. Binds the sugar moieties of pathogen- associated molecular patterns (PAMPs) displayed on microbes and activates the lectin pathway of the complement system. May also activate monocytes through a G protein-coupled receptor, FFAR2, inducing the secretion of interleukin-8/IL-8. Binds preferentially to 9-O-acetylated 2-6-linked sialic acid derivatives and to various glycans containing sialic acid engaged in a 2-3 linkage (By similarity).

Ficolin-2; May function in innate immunity through activation of the lectin complement pathway. Calcium-dependent and GlcNAc-binding lectin (By similarity); Belongs to the ficolin lectin family.

Complement C2a fragment; Component C2 which is part of the classical pathway of the complement system is cleaved by activated factor C1 into two fragments: C2b and C2a. C2a, a serine protease, then combines with complement factor C4b to generate the C3 or C5 convertase; Belongs to the peptidase S1 family.

Complement C3c alpha' chain fragment 1; C3 plays a central role in the activation of the complement system. Its processing by C3 convertase is the central reaction in both classical and alternative complement pathways. After activation C3b can bind covalently, via its reactive thioester, to cell surface carbohydrates or immune aggregates. [C3-beta-c]: Acts as a chemoattractant for neutrophils in chronic inflammation.

Collectin-11; Lectin that plays a role in innate immunity, apoptosis and embryogenesis. Calcium-dependent lectin that binds self and non-self glycoproteins presenting high mannose oligosaccharides with at least one terminal alpha-1,2-linked mannose epitope. Primarily recognizes the terminal disaccharide of the glycan. Also recognizes a subset of fucosylated glycans and lipopolysaccharides. Plays a role in innate immunity through its ability to bind non-self sugars presented by microorganisms and to activate the complement through the recruitment of MAPS1. Also plays a role in apoptosis [...]