Synthesis of four endogenous pyrogens by rabbit macrophages.

Abstract

Endogenous pyrogens were prepared from rabbit peritoneal macrophages. These cells made at least four pyrogens, with pl values of 7.3, 5.2, 5.05, and 5.0. This distribution was observed in supernatants from unfractionated macrophages and also in supernatants from macrophages purified on Ficoll-Hypaque gradients and containing < 1 % neutrophils. All four pyrogens continued to be secreted by macrophages maintained for many hours in tissue culture. The pl 7.3 pyrogen amounted to 10% to 20% of the total pyrogenicity, the pl 5.05 peak about 40%, and the pl 5.2 and 5.0 peaks about 20% each . When endogenous pyrogens were prepared from acute peritonea l exudates, 90% to 95% of the pyrogenicity was found in the pl 7.3 peak. However, 5 % to 10% of the pyrogen focused as three peaks with pl values of 5.2, 5.05, and 5.0 which appeared to be identical wi th the pyrogens secreted by purified macrophages. These four pyrogens had molecular weights of about 14,000 daltons as judged by gel filtration. We saw no evidence of dimer or trimer formation, and there was no evidence of conversion of one pyrogen to another on repeated isoelectric focusings. When macrophages were stimulated in the presence of radiolabeled amino acids , the pl 5.0, 5.05, and 5.2 peaks were radiolabeled. The pyrogens made by macrophages stimulated with endotoxin co-focused with those made by macrophages stimulated with Staphylococcus epidermidis. These results appear to show that macrophages made pyrogen de novo from amino acid precursors and that the same pyrogens were made regardless of the stimulus used to activate the cells. (J LAB CLIN MED 94:95, 1979.)