Stress and chemotherapeutics can negatively affect the immune system of fish in intensive culture. Methods of prevention include immunonutrition. The present study examined the influence of dietary supplementation with the synthetic compound methisoprinol on selected nonspecific immune parameters in intensively cultured juvenile European eel (Anguilla anguilla). The fish were fed a commercial pellet containing 0 (control) or 200 mg methisoprinol/kg feed. After four weeks, the following immunological parameters were measured: respiratory burst activity and potential killing activity of the phagocytes, lymphocyte proliferation after stimulation by concanavaline A or lipopolisaccharide, and serum lysozyme activity, ceruloplasmin activity, total protein, and total immunoglobulin. Except for serum ceruloplasmin activity and total protein, all immune parameters were significantly higher (p<0.05) in the methisoprinol-treated group than in the control, strongly suggesting that four weeks of feeding methisoprinol to juvenile eels might improve innate immunity
