SEARCH Articles Figures Tables FVIII secretion and activation. FVIII is processed as a single-chain peptide, and then cleaved prior to secretion to form a heterodimer consisting of a 90-200 kDa heavy chain, due to limited proteolysis, and an 80 kDa light chain. This heterodimer is the inactive form that circulates in plasma. FVIII is activated [Publishers Imprint]