Western blot analysis of platelet homogenates from a healthy donor and FXIII-deficient patients. Lane 1, Mr marker proteins; lane 2, FXIIIA 2.5 μg; lane 3, partially acivated FXIIIA 2.5 μg; lane 4, homogenate of control platelets, 50 μg protein, lanes 5 and 6, homogenates of FXIII-deficient platelets (patients II-1 and II-3, respectively), 125 μg protein; lanes 7 to 9, same as lanes 4 to 6, but incubated with nonimmune rabbit serum. In both the patients a minute amount of full-length FXIII A-subunit can be detected.