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Decay-accelerating factor
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<p>Complement decay-accelerating factor, also known as CD55 or DAF, is a <a href="/facts/Protein/Jxmagu3E">protein</a> that, in humans, is encoded by the <i>CD55</i> <a href="/facts/Gene/e1swwPY6">gene</a>. </p><p>DAF regulates the <a href="/facts/Complement_system/vRSrQDUv">complement system</a> on the <a href="/facts/Cell_(biology)/bLM9UQvy">cell</a> surface. It recognizes C4b and C3b fragments that are created during activation of C4 (<a href="/facts/Classical_complement_pathway/wtB1DPJn">classical</a> or <a href="/facts/Lectin_pathway/bRNAdBVe">lectin</a> pathway) or C3 (<a href="/facts/Alternative_complement_pathway/eN5PARpC">alternative</a> pathway). Interaction of DAF with cell-associated C4b of the classical and lectin pathways interferes with the conversion of C2 to C2b, thereby preventing formation of the C4b2a <a href="/facts/C3-convertase/yCSPm074">C3-convertase</a>, and interaction of DAF with C3b of the alternative pathway interferes with the conversion of factor B to Bb by factor D, thereby preventing formation of the C3bBb C3 convertase of the alternative pathway. Thus, by limiting the amplification convertases of the complement cascade, DAF indirectly blocks the formation of the <a href="/facts/Membrane_attack_complex/yqyLrl4S">membrane attack complex</a>. </p><p>This <a href="/facts/Glycoprotein/bKPzzW7m">glycoprotein</a> is broadly distributed among <a href="/facts/Hematopoietic/VRDwMymd">hematopoietic</a> and non-hematopoietic cells. It is a determinant for the Cromer blood group system. </p>