The binding of the patient's IgG to FXIII subunits. (A) The binding of patient's IgG to highly purified FXIII-A₂B₂ (●), FXIII-A₂ (▲), or FXIII-B (■) coated to a microtiter plate. (B) The binding of the patient's IgG to FXIII subunits as detected by Western blotting. A and B under the individual lanes indicate FXIII-A and FXIII-B, respectively. SDS PAGE was carried out both in nonreducing and reducing conditions. The arrows on the right and left sides indicate the position of FXIII-A and FXIII-B. Note the difference in the mobility of reduced and nonreduced FXIII-B. The left 2 lanes show Coomassie blue staining of electropherograms of 2.5 μg FXIII-A₂ and FXIII-B. The right lanes demonstrate the detection of 0.5 μg FXIII subunits by Western blotting. Electroblots were incubated with the patient's IgG, and the immune reaction was visualized by biotinylated goat anti–human IgG and avidin-biotinylated peroxidase complex. IgG from the serum of healthy individuals gave no reaction (not shown in the figure).