Synthesis of the first component of human complement in vitro

Isolated segments of human colon and to a lesser extent ileum were capable of synthesizing hemolytically active C'1. This conclusion was based on the following evidence: After elimination of C'1 from tissue with EDTA, we found that segments of the intestinal tract in short-term organ culture showed a 50-1000-fold increase in C'1 activity. The rate of production of C'1 in human intestine was highly temperature dependent; C'1 production was reversibly inhibited by puromycin and actinomycin D. Furthermore, (14)C-labeled amino acids were incorporated into molecules which behaved like C'1. No significant C'1(hu) synthesis was observed in isolated segments of jejunum, stomach, liver, kidney, lung, spleen, lymph node, and thymus.