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Synthesis of factor D by normal human hepatocytes
1Department of Medical Technology, Osaka Prefectural College of Health Sciences, Osaka, Japan.
Background:
Unlike most complement proteins, complement factor D is believed to be synthesized not by the liver but exclusively by adipose tissue.
Method:
Culture supernatants obtained from primary culture of normal human hepatocytes were assayed for factor D by ELISA and analyzed by Western blotting.
Results:
When normal hepatocytes were cultured in protein-free medium without addition of any stimulator for 5 days, factor D was detected in the supernatants at levels as high as 331.07 +/- 41.38 microgram/10(6) cells. Addition of TNF-alpha, IFN-gamma, IL-1beta or LPS to the medium did not result in any distinct effect on the amounts of secreted factor D. Reversible inhibition of factor D secretion by these cells was observed when cultured in the presence of cycloheximide. By immunoblot analysis, secreted factor D exhibited double bands, one with a molecular weight similar to factor D in normal human serum and the other with a slightly larger molecular weight.
Conclusion:
Normal human hepatocytes synthesize factor D constitutively. The liver may be a major source of plasma factor D.