Plasma levels of FXIII-A in thrombocytopenic mice. Blood plasma was obtained from either (A) Bcl-x^Plt20/Plt20 or (B) Mpl^−/− mice (■) or from strain-matched controls () and was assayed for FXIII-A enzyme activity or for FXIII-A antigen levels (by IP with Ab-2 followed by IB with HRP-conjugated sheep anti–FXIII-A antiserum). Results show levels of FXIII-A in the thrombocytopenic mice relative to controls and are based on 6 animals in each group. Insets show immunoblots of immunoprecipitated FXIII-A from pooled plasma.