Physicochemical characterization of cytostatic factors released from human monocytes

Abstract

Cultured human monocytes released cytostatic activity upon in vitro activation with lymphokines and lipopolysaccharide. This activity was mainly due to the presence of 2 different cytostatic factors, termed CstF I and II, which were separated by ion-exchange chromatography. At neutral pH, CstF I bound to the weak anion exchanger DEAE-Sephacel but not to the weak cation exchanger CM-Sepharose; CstF II bound to CM-Sepharose but not to DEAE-Sephacel. The MW of CstF I and II as determined by gel filtration were 55,000 and 40,000, respectively. Upon chromatofocusing, CstF I behaved as if it had an isoelectric point of 5.3. Neither CstF I nor CstF II bound specifically to concanavalin A-Sepharose, indicating the absence of carbohydrate residues containing .alpha.-D-mannopyranosyl, .alpha.-D-glucopyranosyl or sterically related components. Both factors were susceptible to inactivation by proteinase K, demonstrating their protein nature. CstF II was purified more than 3000-fold upon chromatography on CM-Sepharose and Sephacryl S-200. Ion-exchange chromatography and chromatofocusing of CstF I removed 97% of the proteins in the monocyte supernatant, but only 15% of the activity was recovered, resulting in a 5-fold purification of CstF I.