C-reactive protein in eel: purification and agglutinating activity.

Area of Science:

• Biochemistry
• Immunology
• Marine Biology

Background:

• C-reactive protein (CRP) is a key acute-phase protein involved in innate immunity.
• CRP levels can indicate inflammation and infection in various species.
• Characterizing CRP in non-mammalian vertebrates like fish provides insights into immune system evolution.

Purpose of the Study:

• To highly purify C-reactive protein from Japanese eel (Anguilla japonica) serum.
• To characterize the biochemical and functional properties of eel C-reactive protein (eCRP).
• To investigate the potential immune functions of eCRP.

Main Methods:

• Purification of eCRP using phosphatidyl-choline and Ca2+ precipitation.
• Analysis of molecular weight and structure using SDS-PAGE and gel filtration.
• Assessment of agglutinating activity against Streptococcus pneumoniae and rabbit red blood cells.
• Immunoelectrophoresis to determine eCRP's location in serum.
• Precipitin reactions with various polycations.

Main Results:

• Highly purified eCRP with distinct molecular weights under reducing and non-reducing conditions.
• eCRP demonstrated Ca2+-dependent agglutinating activity against Streptococcus pneumoniae, inhibited by phosphorylcholine.
• eCRP agglutinated rabbit red blood cells, with inhibition by glucosamine or mannose.
• eCRP formed precipitin lines with histone, protamine, and polycations.
• Serum eCRP levels in Japanese eels ranged from 6.8 ng/ml to 5.3 mg/ml, with a mean of 834 ng/ml.

Conclusions:

• Japanese eel C-reactive protein (eCRP) is a distinct protein with characteristics similar to mammalian CRP.
• eCRP exhibits functional activities, including bacterial and hemagglutinating properties, suggesting a role in innate immunity.
• The characterization of eCRP provides valuable data for comparative immunology and understanding fish immune responses.