CYCLIC-NUCLEOTIDE CHANGES INDUCED IN HUMAN-LEUKOCYTES BY A PRODUCT OFAXENICALLY GROWN ENTAMOEBA-HISTOLYTICA THAT INHIBITS HUMAN MONOCYTE LOCOMOTION

Pulse exposure of human mononuclear phagocytes to the monocyte locomot ion-inhibitory factor produced by Entamoeba histolytica (i.e., the 369 - to 765-Da chromatographic fraction obtained from the supernatant flu id of axenically grown E. histolytica) led to a swift increase in the intracellular concentration of adenosine 3':5' cyclic monophosphate (c AMP). A weaker response was observed in human polymorphonuclear leukoc ytes, the locomotion of which, however, is not inhibited by this amebi c factor. The same chromatographic fraction obtained from the axenic m edium control lacked this effect, at least upon mononuclear phagocytes . On the other hand, both the monocyte locomotion-inhibitory factor an d the axenic medium control, possibly through shared culture medium co mponents, induced comparable increases in guanosine 3':5' cyclic monop hosphate (cGMP) in human mononuclear phagocytes and in polymorphonucle ar leukocytes, thus suggesting that the latter nucleotide is not criti cal for the leukotactic inhibitory phenomenon. Our results suggest tha t like other leukotactic inhibitors, the monocyte locomotion-inhibitor y factor produced by E. histolytica operates through modulations of in tracellular cAMP