Effect of flumequine on peripheral blood leukocytes, alpha naphthyl acetate esterase activity and mitogenic lymphocyte response

The aim of this study was to evaluate the effect of flumequine on the percentage of peripheral blood leukocytes of carp, alpha naphthyl acetate esterase (ANAE) activity and proliferative activity of lymphocytes stimulated with concanavalin A (Con A) and lipopolysaccharide (LPS). Flumequine was administered to 40 carp, weighing 150 +/- 10 g, at a dose of 12 mg/kg, once (group I) and four times, every 2 days (group II). Among white blood cells in flumequine, treated fish (group II) observed a decrease in percentage of lymphocytes and an increase of neutrophiles. Identification of the ANAE esterase activity in fish lymphocytes of the control group showed the advantage of positive cells over the negative ones and amounted to 62.65 +/- 3.22%. After administration of flumequine in group II fish, this value decreased to 44.75 +/- 3.70%. The present study clearly demonstrated that both Con A and LPS induced lymphoid cell proliferation in vitro in group I. There was an increase in activity after stimulation of LPS and its reduction after Con A in group II. This indicates a stimulating effect of flumequine on B lymphocytes. The results of this study are not conclusive as to the positive effect of the drug on the immune system of fish and indicate the need for caution in its use.