FXIIIa does not crosslink fibrin to RBCs. Clotting was initiated in recalcified (5 mM, final) PRP (−RBCs) or whole blood (+RBCs) with thrombin (20 nM, final), in the absence or presence of T101 (200 μM, final). Clots were then dissolved and fibrin crosslinking patterns were analyzed by western blotting using a polyclonal anti-human fibrinogen antibody. Representative blot of n = 4 experiments.