Factor VIII

Coagulation factor VIII (Factor VIII, FVIII, also known as anti-hemophilic factor (AHF)) is an essential <a href="/facts/Blood_clotting/vnfEevM0">blood clotting</a> <a href="/facts/Protein/Jxmagu3E">protein</a>. In humans, it is encoded by F8 <a href="/facts/Gene/e1swwPY6">gene</a>. Defects in this gene result in <a href="/facts/Hemophilia_A/Bx8rkF4c">hemophilia A</a>, an X-linked <a href="/facts/Bleeding_disorder/1qchdP31">bleeding disorder</a>. 
Factor VIII is produced in the <a href="/facts/Liver/Rtp4Fk2b">liver</a>'s <a href="/facts/Liver_sinusoid/xPAbmGVT">sinusoidal cells</a> and <a href="/facts/Endothelial/L4ENFVnw">endothelial</a> cells outside the liver throughout the body. This protein circulates in the bloodstream in an inactive form, bound to another molecule called <a href="/facts/Von_Willebrand_factor/64IHfEJ9">von Willebrand factor</a>, until an <a href="/facts/Injury/PJ7CbnMQ">injury</a> that damages <a href="/facts/Blood_vessel/FG3GjPNW">blood vessels</a> occurs. In response to injury, coagulation factor VIII is activated and separates from von Willebrand factor. The active protein (sometimes written as coagulation factor VIIIa) interacts with another coagulation factor called factor IX. This interaction sets off a chain of additional chemical reactions that form a blood clot.
Factor VIII participates in <a href="/facts/Blood_coagulation/vnfEevM0">blood coagulation</a>; it is a cofactor for <a href="/facts/Factor_IX/s45WpX2A">factor IXa</a>, which, in the presence of Ca2+ and <a href="/facts/Phospholipid/u6GhNCF5">phospholipids</a>, forms a complex that converts <a href="/facts/Factor_X/7IQfSlKM">factor X</a> to the activated form Xa. The factor VIII gene produces two alternatively spliced transcripts. Transcript variant 1 encodes a large <a href="/facts/Glycoprotein/bKPzzW7m">glycoprotein</a>, isoform a, which circulates in plasma and associates with von Willebrand factor in a noncovalent complex. This protein undergoes multiple cleavage events. Transcript variant 2 encodes a putative small protein, isoform b, which consists primarily of the phospholipid binding domain of factor VIIIc. This binding domain is essential for coagulant activity.
People with high levels of factor VIII are at increased risk for <a href="/facts/Deep_vein_thrombosis/vX7cGv8J">deep vein thrombosis</a> and <a href="/facts/Pulmonary_embolism/LPjKCPba">pulmonary embolism</a>. Copper is a required cofactor for factor VIII and copper deficiency is known to increase the activity of factor VIII.
<a href="/facts/Factor_VIII_(medication)/XyoW8Cwv">Factor VIII</a> is available as a medication that is on the <a href="/facts/WHO_Model_List_of_Essential_Medicines/6kmu81Xm">WHO Model List of Essential Medicines</a>, the most important medications needed in a basic <a href="/facts/Health_system/LpM7ISXR">health system</a>.

Factor VIII open-in-new

Factor VIII