In vitrodegradation ofAeromonas salmonicidaandLimulus polyphemushemocyanin by Atlantic salmon,Salmo salarL. macrophages

Cultivated Atlantic salmon head kidney macrophages endocytosed and digested iodinated formaldehyde-fixedAeromonas salmonicidaantigens effectively. The degradation was time-dependent as demonstrated by increased acid soluble radioactivity obtained in macrophage media with time after the addition of antigens. Gel chromatography of the degraded material revealed a peak of radioactivity corresponding to molecular weights between 1000 and 6500 Da.In vitrodegradation ofLimulus polyphemushemocyanin (LPH) adsorbed to mineral particles was less efficient compared to the degradation of whole bacterial cells, whereas degradation of soluble LPH was negligible. There were no significant differences in the rate of processing at 4 (6), 12 and 18°C. Inhibition studies using ammonium chloride, a substance that raises the pH of endosomes and lysosomes, showed decreased intracellular degradation ofA. salmonicidain a dose-dependent manner. Monensin, a substance reported to block receptor-mediated phagocytosis, very effectively reduced the extent of processing whereas leupeptin and pepstatin, specific inhibitors of the major classes of cysteine and aspartic proteinases respectively, only slightly affected the processing.