Factor XIII levels in the patient's plasma and platelets, and the fate of factor XIII added to the patient's plasma in vitro and in vivo. (A) Factor XIII activity and antigen levels in the patient's plasma and platelet lysate. Results on plasma FXIII activity and FXIII antigens are expressed as a percentage of normal plasma content. Mean plasma FXIII activity and antigen values of more than 100 healthy individuals were considered as normal plasma FXIII activity and antigen concentrations.16,17 Platelet FXIII activity and FXIII-A antigen are expressed as a percentage of mean FXIII activity and FXIII-A antigen measured in platelet lysates from 10 healthy individuals. ND indicates not determined. (B) FXIII-A antigen in the patient's platelets as detected by Western blotting. Platelet protein (50 μg) was subjected to SDS PAGE. FXIII-A was detected by affinity purified sheep anti–FXIII-A antibody (Affinity Biologicals, Ancaster, ON), biotinylated rabbit anti–sheep IgG, and avidin-biotinylated peroxidase complex (Vector). Std indicates FXIII-A2 purified from human platelets; N, lysate of normal platelets; and P, lysate of the patient's platelets. (C) The recovery of various concentrations of purified plasma FXIII incubated with the patient's plasma in vitro. The amounts of added and recovered FXIII are expressed as a percentage of average normal plasma FXIII activity. The equation and the “r” value of the straight line demonstrate full recovery in the whole concentration range. (D) Plasma FXIII activity at various intervals following the administration of 3750 U Fibrogammin-P to the patient. The horizontal broken line represents half-maximal FXIII activity; the vertical dotted line shows the time when half of the added FXIII activity was eliminated from the circulation.
