Fish immunology. II. Morphologycal and cytochemical characterization and phagocytic activities of head kidney macrophages from rainbow trout (Salmo gairdneri Richardson)

In Salmo gairdneri Richardson trouts, a comparison was made between macrophages (MO) derived from head kidney and peripheral blood monocytes. Morphologically and cytochemically no differences were observed between these two types of mononucleated cells. On the other hand, in parallel studies the ability of trout erythrocytes to engulf Candida albicans (CA) was evaluated and compared to the MO phagocytosis. In erythrocytes, engulfment is preceded by binding to CA and cell membrane invagination, while this was not the case for MO. Finally, MO stimulated with lipopolysaccharides (LPS) did not modify their phagocytic capacities, thus suggesting a lack of LPS receptors or a tolerance to LPS.