Association of plasma IgM with body size, histopathologic changes, and plasma chemistries in adult Pacific herring Clupea pallasi

Pacific herring Clupea pallasi immunoglobulin is an IgM-like molecule comprised of heavy and light chains with molecular weights of 79 and 25 to 27 kD, respectively. Purified immunoglobulin was used to generate highly specific polyclonal antibodies for development of a sandwich ELISA. The ELISA was used to quantify total plasma IgM in 602 Pacific herring captured in Prince William Sound and Sitka Sound, Alaska, USA. Plasma IgM concentrations ranged from 0.13 to 5.32 mg ml-1. Using multiple stepwise regression analysis, plasma IgM was highly correlated (p < or = 0.01) with body length, Ichthyophonus hoferi infection, plasma albumin, plasma cholesterol, liver macrophage aggregates, and focal skin reddening. I. hoferi was the only organism significantly associated with plasma IgM. Gender, site, and season (spring vs fall) did not contribute to significant differences in plasma IgM. This study contributes to the understanding of the interaction of body size, plasma chemistries, and pathological changes upon circulating immunoglobulins in fish.