Fibrin crosslinking by noncomplexed free FXIII-A₂remaining in the plasma after removal of FXIII-A₂B₂complex by immunodepletion. Plasma was depleted of FXIII-A₂B₂ and FXIII-B₂ by immunoabsorption on Sepharose-linked anti-FXIII-B monoclonal antibody that reacted with both free and complexed FXIII-B. Depleted plasma (DP) and normal plasma (P) were clotted by thrombin (T) in the presence and absence of the FXIIIa inhibitor iodoacetamide (IA). Depleted plasma was also clotted by batroxobin (B) in the presence of the thrombin inhibitor hirudin (H). The fibrin clots were washed and analyzed by SDS-PAGE; fibrin α, β, and γ chains; γ-chain dimers (γ-γ); and high-M_r α-chain polymers (α_p) are indicated on the figure. The table below the gel shows the components of the clotting mixture that resulted in the fibrin clot shown on the respective lane.