Seasonal variations in the immune system of the cyprinid Tinca tinca. Phagocytic function.

Seasonal variations in the in vitro phagocytic process of blood granulocytes from the tench Tinca tinca were examined. Different stages of the phagocytic process: mobility rate, attachment, ingestion and killing of Candida albicans were evaluated. Tench were kept in natural ponds in ambient water temperature, and the in vitro assays were performed at both 22 degrees C and the relative ambient temperature. Results between the seasonal samples were then compared. In vitro induced mobility, attachment, ingestion and killing of C. albicans showed strong seasonal variations, furthermore, the phagocytic process at 22 degrees C varied significantly according to season. Phagocytic activity from samples taken during the spring demonstrated the highest activity at 22 degrees C, whilst greatest activity at seasonal temperature, in terms of mobility rate, phagocytic index and microbicide capacity, occurred during the winter. These results are consistent with the hypothesis that phagocytosis in fish is resistant to low temperatures.