Differential effects of temperature on specific and nonspecific immune defences in fish.

The susceptibility of fish to disease is partly dependent on their environment, in particular on water temperature. It is generally accepted that lower temperatures adversely affect specific immune responses mediated by T helper cells. The probable mechanisms involved in such suppression in teleost fish are reviewed. Furthermore, the effects of temperature on nonspecific defences, such as phagocytosis and cytotoxicity, are described and total immune competence in teleosts at low environmental temperatures is discussed.