Age-0 striped bass, Morone saxatilis (Walbaum, 1792), response to immunostimulation

Summary Young-of-the-year (age-0) striped bass, Morone saxatilis, were studied to characterize their responses to inflammatory stimuli. There were two studies, with the hypotheses that (i) 24 h in larger fish. Study I was conducted to understand the cytokine expression pattern (IL-1β, TNF-α, Nramp and TGF-β) in response to lipopolysaccharide (LPS) or Freund's complete adjuvant (FCA) stimulation in age-0 striped bass (3.44 ± 1.68 g, 70.6 ± 10.3 mm fork length) up to 24 h post injection (hpi). Study II was similar to Study I, but striped bass were sampled over a longer time frame (by 48 hpi) and larger age-0 striped bass were used (20.6 ± 5.9 g, 129.2 ± 10.9 mm fork length). It was confirmed that immunostimulants such as LPS and FCA induce production of inflammatory cytokines and Nramp, which are important in innate immune response to bacterial infection. The responses were rapidly stimulated with LPS (IL-1β, TNF-α, TGF-β >3-fold increase, compared to PBS) or FCA (IL-1β >3-fold and TGF-β >2-fold, compared to PBS) within 6 hpi and maintained in most cases 48 hpi (spleen Nramp and TGF-β 2-fold >PBS, at 24 and 48 h), similar to other teleosts. Intraperitoneal injection with PBS also simulated inflammatory gene expression, but was delayed (IL-1β, TNF-α, TGF-β and Nramp, FCA and LPS LPS and PBS) in comparison to LPS and FCA, suggesting that this procedure and possibly the volume used can be stimulatory and potentially harmful in age-0 fish. Therefore, this study suggests that age-0 striped bass are capable of strong cytokine induction in response to immunological stimulation within a very short period of time.