Content deleted Content added
Reverted to revision 886745442 by Citation bot (talk): Reference hijacking, and DOI does not link to the article named in the citation (TW) |
Disambiguated: IgG → Immunoglobulin G (2) |
||
Line 77:
The '''complement component 1q''' (or simply '''C1q''') is a [[protein complex]] involved in the [[complement system]], which is part of the [[innate immune system]]. C1q together with [[C1r]] and [[C1s]] form the [[C1 complex]].
[[Antibody|Antibodies]] of the [[adaptive immune system]] can bind [[antigen]], forming an [[antigen-antibody complex]]. When C1q binds antigen-antibody complexes, the [[C1 complex]] becomes activated. Activation of the C1 complex initiates the [[classical complement pathway]] of the complement system. The antibodies [[IgM]] and all [[Immunoglobulin G|IgG]] subclasses except [[Immunoglobulin G#Subclasses|IgG4]] are able to initiate the complement system.
==Structure==
Line 97:
It is potentially [[Valence (chemistry)|multivalent]] for attachment to the complement fixation sites of [[immunoglobulin]].
The sites are on the CH2 ___domain of [[Immunoglobulin G|IgG]] and, it is thought, on the CH4 ___domain of [[IgM]]. IgG4 cannot bind C1q, but the other three IgG types can.
The appropriate [[peptide sequence]] of the complement fixing site might become exposed following complexing of the immunoglobulin, or the sites might always be available, but might require multiple attachment by C1q with critical geometry in order to achieve the necessary [[avidity]].
| |||