Bovine early pregnancy factor (EPF) activity dependent on a 67-kDa polypeptide

Area of Science:

• Reproductive immunology
• Maternal-fetal interface
• Protein biochemistry

Background:

• Early pregnancy factor (EPF) is a crucial immunosuppressive protein facilitating successful pregnancy.
• Identifying EPF and its role in bovine reproduction is vital for understanding pregnancy maintenance.

Purpose of the Study:

• To isolate and characterize the bovine early pregnancy factor (EPF).
• To investigate the presence and activity of EPF in pregnant versus non-pregnant cows.
• To explore the antigenic differences between EPF in pregnant and non-pregnant states.

Main Methods:

• Serum fractionation and polypeptide enrichment from pregnant and non-pregnant cows.
• Molecular weight determination (67 kDa) and protein labeling (125I, peroxidase).
• Rosette inhibition test for EPF activity assessment.
• Monoclonal and polyclonal antibody production and characterization (HPLC, SDS-PAGE).

Main Results:

• A 67-kDa polypeptide with EPF activity was isolated from pregnant cow serum.
• An inactive 67-kDa polypeptide (pre-EPF) was identified in non-pregnant cow serum.
• Monoclonal antibodies could not differentiate between pregnant and non-pregnant 67-kDa polypeptides.
• Mouse anti-EPF serum distinguished between pregnant and non-pregnant 67-kDa polypeptides, revealing different antigenic determinants.
• A second, higher molecular weight protein was detected in both states.

Conclusions:

• Bovine EPF is a 67-kDa polypeptide present in pregnant cows, with an inactive precursor in non-pregnant cows.
• Distinct antigenic properties of the 67-kDa polypeptides indicate structural differences between pregnant and non-pregnant states.
• These findings provide the first evidence of antigenic differences in EPF-related proteins, aiding in pregnancy diagnostics.