FXIII-A₂ is not required for FXIII-B₂ secretion from mouse liver. Serum alkaline phosphatase (ALP) (A), alanine transaminase (ALT) (B), and aspartate transaminase (AST) (C) levels were determined in F13a1^+/+, F13a1^+/−, and F13a1^–/– mice; liver weight (D) in F13a1^+/+, F13a1^+/−, and F13a1^–/– mice, reported as a percentage of body weight. Dots represent individual mice, bars show mean ± standard deviation. Groups were compared by 1-way ANOVA with Dunnett post hoc testing (A-D). (E) Histology of liver tissue from F13a1^+/+, F13a1^+/−, and F13a1^–/– mice. Sections were stained with hematoxylin and eosin. Representative low (top) and high (bottom) magnification images are shown. Scale bar indicates 100 μm (top) and 20 μm (bottom). (F) FXIII-B antigen in liver tissue lysates from F13a1^+/+, F13a1^–/–, and rFXIII-A₂–treated F13a1^–/– was visualized by immunoblotting with anti–FXIII-B antibody. Lysates were normalized by protein concentration and the same amount of total protein was loaded for each sample. Each lane shows 1 mouse. Recombinant FXIII-B (rFXIII-B) was included as a standard. ANOVA, analysis of variance; ns, nonsignificant; U/L, units/liter.