Biosynthesis of complement components by cultured rat hepatocytes.

Area of Science:

• Biochemistry
• Immunology
• Cell Biology

Background:

• The complement system is crucial for innate and adaptive immunity.
• Understanding the synthesis of complement components is vital for immunology research.

Purpose of the Study:

• To investigate the synthesis of complement components by rat hepatocytes in vitro.
• To analyze the processing of complement proteins C3 and C4 during synthesis.

Main Methods:

• Isolation and in vitro culture of hepatocytes from Charles River rats.
• Analysis of synthesized proteins including albumin and complement components (C4, C2, C3, B).
• Pulse-labeling studies using [35S]methionine to track protein synthesis and processing.

Main Results:

• Hepatocytes synthesized albumin and complement components C4, C2, C3, and B.
• Complement component 4 (C4) and complement component 3 (C3) were synthesized as single polypeptide chains.
• Pro-C4 was not converted to its plasma form intracellularly, while pro-C3 was processed into alpha- and beta-chains.

Conclusions:

• In vitro culture of rat hepatocytes is a valuable model for studying complement component synthesis.
• The study provides insights into the intracellular processing of complement components C3 and C4.