The binding of anti-FXIII-B(2) antibody to recombinant FXIII-B and its combined 1+2 sushi domains (SD1+2). FXIII-B and SD1+2 were expressed in insect cells as described in the text. Cell culture supernatants were concentrated and analyzed by western blotting. Lane 1: FXIII-B isolated from the plasma (the faint band below FXIII-B corresponds to a proteolytic product); lane 2: supernatant of cultured cells expressing rFXIII-B; lane 3: supernatant of mock-transfected cells; lane 4: supernatant of cells expressing SD1+2.