Comparison of the Immune Response of Striped Bass and Hybrid Bass

We developed methods for examining the pathophysical response of striped bass and hybrid bass to various forms of stress. This involved development of techniques for the measurement of lysozyme, mitogen blastogenesis, mixed lymphocyte reaction, and oxidative burst, which are important general indicators of systemic immune function. We also examined local immune defenses (epithelial integrity), as well as homeostatic indicators in blood, including osmotic balance and glucose. Acute stress resulted in significant perturbations in a number of parameters, including glucose, electrolytes, osmolarity, lysozyme, and mixed lymphocyte reaction. Most significantly, acute confinement stress resulted in severe damage to the epidermal epithelium, as indicated by the rapid (within 2 hr) development of erosions and ulcerations on various fins. There were significant differences in the resting levels of some immune functions between striped bass and hybrid bass, including response to mitogens in the leukocyte blastogenesis test. Our studies also revealed that there were significant differences in how striped bass and hybrid bass respond to stress, with striped bass being much more severely affected by stress than the hybrid. This was reflected in more severe changes in glucose, cortisol dynamics, and plasma lysozyme. Most significantly, striped bass developed more severe idiopathic skin ulceration after stress, which may be a major reason why this fish is so prone to develop opportunistic bacterial and fungal infections after stress. Hybrid bass injected with equine serum albumin developed a typical humoral immune response, with peak antibody production 28 days after primary immunization. Fish that were exposed to a chronic stress after a primary immunization showed almost complete inhibition of antibody production.