Immunochemical studies of human factor XIII

Area of Science:

• Biochemistry
• Immunology
• Hematology

Background:

• Plasma factor XIII (FXIII) is a tetrameric zymogen (a2b2) involved in blood coagulation.
• The FXIII b subunit may function as a carrier for the catalytically active a subunit.
• Understanding subunit interactions is key to FXIII function.

Purpose of the Study:

• To develop a sensitive and specific radioimmunoassay (RIA) for quantifying the FXIII b subunit.
• To investigate the concentration of the FXIII b subunit in human plasma and serum.

Main Methods:

• Purified FXIII was treated with thrombin and chromatographed to isolate subunits.
• A monospecific antiserum was generated using the purified b subunit.
• A RIA was established and validated for measuring b subunit concentrations in purified samples, plasma, and serum.

Main Results:

• The developed RIA demonstrated a linear range of 7-700 ng/ml with high sensitivity.
• The assay accurately quantified the b subunit in both purified preparations and biological samples.
• Mean b subunit concentration in normal human plasma was determined to be 13.8 µg/ml, with a similar concentration in serum.

Conclusions:

• A robust RIA for the FXIII b subunit has been successfully developed.
• The RIA is suitable for determining b subunit levels in plasma and serum.
• The b subunit is quantitatively recovered during serum coagulation, indicating its stability.