Light and electron microscopic studies on the enzyme cytochemistry of leucocytes of eels, Anguilla species

The leucocytes of three anguillid eels were studied using enzyme cytochemistry. Leucocytes were stained for peroxidase, alkaline phosphatase, acid phosphatase, aryl sulphatase, β-glucuronidase, N-acetyl-β-glucosaminidase, β-galactosidase, lysozyme, a variety of non-specific esterases, chloroacetate esterase and two proteases. All cells were negative for aryl sulphatase, β-glucuronidase, N-acetyl-β-glucosaminidase, and β-galactosidase. Very few neutrophils, thought to be mature, and all eosinophils contained peroxidase-positive granules, and some monocytes showed very weak peroxidase staining. All leucocytes lacked alkaline phosphatase, but all cells except lymphocytes and thrombocytes of A. dieffenbachii contained acid phosphatase. Neutrophil acid phosphatase released into phagosomes was associated with Escherischia coli bacteriolysis. Neutrophils also secrete lysozyme and, with monocytes, produce and secrete a variety of esterases. The possible interaction of lysozyme, acid phosphatase and esterases in bacteriolysis is discussed.