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A heterotrimeric protein complex composed of complement component 8 (C8) chains alpha, beta and gamma. The alpha and gamma chains form a disulfide-linked dimer that is noncovalently associated with the beta chain. C8 inserts itself into target cell membranes following formation of the C5b-6-7 complex and then recruits 10-16 molecules of C9 to complete the formation of the membrane attack complex.
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Complement component-4 (1744 aa, ~193 kDa) is part of the complement cascade, which mediates the innate immune response to infection. The full length protein is a precursor that is secreted as a trimeric molecule containing an alpha, beta and gamma chain. When the complement cascade is initiated, the protein is cleaved. This proteolysis releases both the alpha chain, C4 anaphylatoxin, which stimulates inflammation, and a dimer of the beta and gamma chains, which mediates the interaction between the antigen-antibody complex and other complement components.
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A fibrin breakdown fragment — most useful for ruling out venous thromboembolism when clinical probability is low.
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IgA is the immunoglobulin subclass that is associated with antibody-mediated mucosal immunity. It is secreted as dimers into the mucosa and is the most effective isotype at fixing complement by the alternative pathway, even though it lacks the ability to fix complement by the classical pathway. There are two subtypes in the human - IgA1 and IgA2.
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Gonadal glycoprotein hormone, Inhibin A, consists of an alpha subunit covalently linked to a beta-A subunit and strongly inhibits pituitary FSH secretion. Serum concentrations transit during the menstrual cycle. Dimers of the beta subunit (a TGF-beta superfamily member), termed activin, are potent stimulators of FSH secretion. (from OMIM 147380 and NCI)