Why would mixing blood from a boy with Factor IX deficiency with a haemophiliac who has Factor VIII deficiency clot?

Why would mixing blood from a boy with Factor IX deficiency with a haemophiliac who has Factor VIII deficiency clot?

• A. Factor IX alone can clot.
• B. The mixture contains both active Factors, enabling the pathway to clot.
• C. Factor VIII alone can clot.
• D. The mixture dilutes clotting.

Answer: (B)

Coagulation via the intrinsic pathway needs more than one factor working together. Factor IX becomes IXa and, with Factor VIIIa, forms a complex that activates Factor X to Xa. This step is essential to generate enough thrombin to form a stable clot. If one person lacks Factor IX and another lacks Factor VIII, mixing their blood provides both missing components, so the tenase complex can form and the cascade can proceed to clotting. Having only Factor IX present wouldn’t be enough because Factor VIII is still missing to form the active complex. Similarly, Factor VIII alone wouldn’t clot since Factor IXa is needed to partner with VIIIa. Dilution doesn’t improve clotting; it reduces the concentration of necessary factors.

Coagulation via the intrinsic pathway needs more than one factor working together. Factor IX becomes IXa and, with Factor VIIIa, forms a complex that activates Factor X to Xa. This step is essential to generate enough thrombin to form a stable clot. If one person lacks Factor IX and another lacks Factor VIII, mixing their blood provides both missing components, so the tenase complex can form and the cascade can proceed to clotting.

Having only Factor IX present wouldn’t be enough because Factor VIII is still missing to form the active complex. Similarly, Factor VIII alone wouldn’t clot since Factor IXa is needed to partner with VIIIa. Dilution doesn’t improve clotting; it reduces the concentration of necessary factors.