ELICITATION OF MACROPHAGES FROM THE PERITONEAL-CAVITY OF CHANNEL CATFISH

Four chemicals were evaluated for elicitation of macrophages in perito neal cavities of 250-300g healthy channel catfish Ictalurus punctatus. Cellular exudates were collected at 3, 5, 7, 10, 14, and 20 d followi ng intraperitoneal injections with squalene, Freund's incomplete adjuv ant (FIA), goat serum, thioglycollate, or as a control, phosphate-buff ered saline. Injection with either squalene or FIA induced significant ly greater (P less than or equal to 0.0001) macrophage recruitment tha n the other chemicals. The effectiveness of squalene and FIA was compa red further by macrophage collection daily for 7 d. Squalene and FIA e licited similarly high macrophage responses (P less than or equal to 0 .0450), the highest being 3.43 x 10(6) macrophages/mL (SE, 2.4 x 10(6) ) at 99% purity at day 2 and 2.1 x 10(6) macrophages/mL (SE, 0.7 x 10( 6)) at day 14 at 80% purity, respectively. In both experiments, the ti me after injection was not statistically significant, nor was there an interaction between time and chemicals. The occurrence of cells other than macrophages decreased with time to yield macrophage recoveries o f 47-99% for squalene and 30-80% for FIA. Two subsets of macrophages w ere observed by means of flow cytometry. As demonstrated by chemilumin escence, the squalene-elicited cells produced high-energy oxygen compo unds important to the phagocytic process.