FXIII-A₂ increases circulating FXIII-B in mice. (A) FXIII-A and -B in F13a1^+/+, F13a1^+/−, and F13a1^–/– mouse plasma were visualized using immunoblotting with anti-FXIII-A and -B antibodies, respectively. Each lane shows plasma from 1 mouse. (B) FXIII-B band intensity was quantified using densitometry. Each dot represents 1 mouse, and lines show mean ± standard deviation. Groups were compared by 1-way ANOVA with Dunnett post hoc testing, ∗∗∗∗ P < .0001. (C) Schematic of in vivo rFXIII-A₂ infusion model. F13a1^–/– mice (aged 8-12 weeks) were infused with rFXIII-A₂ (4 mg/kg) via the tail vein, and blood was collected at various times after infusion. (D) At the indicated times after infusion, plasma FXIII-A and -B antigen was visualized by immunoblotting with anti-FXIII-A and anti-FXIII-B antibodies, respectively. Representative blots are shown. (E) FXIII-A and (F) FXIII-B were quantified using densitometry and normalized to subunit levels immediately after infusion (determined from samples collected within 1 minute of infusion, indicated as the 0-hour timepoint). Dots represent means ± standard error, N = 3-18 per time point. ANOVA, analysis of variance; A.U., arbitrary units.