Changes in Peripheral Blood Leukocyte Percentages and Function of Neutrophils in Stressed Channel Catfish

Abstract

Channel catfish Ictolwrus punctotus were subjected to a simulated handling (including bleeding) and transport stress. Using flow cytometry in conjunction with monoclonal antibodies to channel catfish B and T lymphocytes (minimal cross-reaction with thrombocytes) and neutrophils coupled with routine hematological methods, we demonstrated significant decreases in the percentage of B lymphocytes and increases in T lymphocytes and neutrophils of transported fish, yet there was no change in neutrophil phagocytic function. These data suggest that the length of the stressing event or the duration of exposure of the neutrophils to cortisol could determine if immune responses become suppressed. These data prompted us to expose channel catfish in vivo, and isolated neutrophils in vitro, to cortisol at various concentrations and for various time periods. Exposure of neutrophils to cortisol concentrations of 100 jtg/dL for 2 h did not suppress phagocytosis; however, significant decreases in the percent phagocytosis and bacterial killing and increases in total number of neutrophils isolated were obtained after repeated in vivo administration of cortisol. The results of these experiments indicate (1) that bleeding, handling, and transport of channel catfish induce a characteristic relative lymphopenia and neutrophilia, (2) that cortisol does not act alone to induce suppression of phagocytic function (based on the in vitro administration of cortisol), and (3) that high physiological concentration of cortisol in vivo can initiate phagocytic suppression. In general, the intraperitoneal cortisol injection experiments suggested that stress on channel catfish that produces a concomitant high serum concentration of cortisol can suppress neutrophil phagocytic function, perhaps providing an avenue for the onset of infection.Stress and disease can lead to many alterations in immune function (Griffin 1989). Many stressors present in the aquatic environment play ma-

Handling, confinement and anaesthetic exposure induces changes in the blood and tissue immune characteristics of gilthead sea bream

“…The expected changes induced by these 2 stressors were clearly observed (Pickering et al 1982, Ellsaesser & Clem 1986, Fletcher 1986, Bly et al 1990, Ainsworth et al 1991. In addition, the presence of an anaesthetic reversed or delayed most of the changes, suggesting that the anaesthetic plays a protective role.…”

“…Rowley et al (1988) reported that the granulocyte function is an important non-specific defense in fish. Fish heterophilic granulocytes have been described as active ameboid and phagocytic cells (Morrow & Pulsford 1980, Hyder et al 1983, which serve as a first line of cell-mediated defense (Ainsworth et al 1991). The observed effect is likely caused by the activation of the pituitary-adrenal axis.…”

Fasted and postprandial response of serum physiological response, hepatic antioxidant abilities and HSP70 expression in Wuchang bream (Megalobrama amblycephala) fed different dietary carbohydrate levels

“…The nonspecific defense mechanisms of fish include neutrophil activation, production of peroxidase and oxidative free radicals, and initiation of other inflammatory factors (Ainsworth et al, 1991). The stress response might also impact factors such as total antioxidation capacity and levels of SOD, MDA and various peroxidases (Itou et al, 1996;Liu et al, 2010).…”

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“…Although no significant increase of MCV and MCH in anaesthetic exposed fish was observed in the present study, it seems that the same phenomena was observed, however, less sever. According to Ainsworth et al (1991), acute stress in fish is usually followed by a decrease of the percentage of lymphocytes and eosinophiles and an increase in neutrophiles contribution in circulating blood. Cortisol, secreted during stress reaction, shortens the life span of lymphocytes and promotes their apoptosis (Wyets et al 1998, Verburg van Kemenade 1999.…”