Complement component 1q

<p>The complement component 1q (or simply C1q) is a <a href="/facts/Protein_complex/GW11Ee34">protein complex</a> involved in the <a href="/facts/Complement_system/vRSrQDUv">complement system</a>, which is part of the <a href="/facts/Innate_immune_system/lz4BpSQI">innate immune system</a>. C1q together with <a href="/facts/C1r/1uAHj44r">C1r</a> and <a href="/facts/C1s/k7fTGw62">C1s</a> form the <a href="/facts/C1_complex/zz0uv0tc">C1 complex</a>.
</p><p><a href="/facts/Antibody/MX8pdTdP">Antibodies</a> of the <a href="/facts/Adaptive_immune_system/bc7zT1Jo">adaptive immune system</a> can bind <a href="/facts/Antigen/9JlAernG">antigen</a>, forming an <a href="/facts/Antigen-antibody_complex/s4kKT3lc">antigen-antibody complex</a>. When C1q binds antigen-antibody complexes, the <a href="/facts/C1_complex/zz0uv0tc">C1 complex</a> becomes activated. Activation of the C1 complex initiates the <a href="/facts/Classical_complement_pathway/wtB1DPJn">classical complement pathway</a> of the complement system. The antibodies <a href="/facts/IgM/23PjpgIQ">IgM</a> and all <a href="/facts/Immunoglobulin_G/cKzc83tk">IgG</a> subclasses except <a href="/facts/Immunoglobulin_G/cKzc83tk">IgG4</a> are able to initiate the complement system.
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Complement component 1q open-in-new

Complement component 1q