Short-term nutrient deprivation affects immune function

Measurement of insect immune effector system function aimed at identifying costs has largely been stimulated by the ideas of Hamilton & Zuk (1982), who proposed that choosy females may derive some genetic benefit from selecting parasite-resistant males. Field studies of such systems assume that most variation in measured immune traits is affected strongly by genes and pay little attention subsequently to the role of nutritional status in determining the magnitude of assayed immune effector systems. In this paper the effects of nutrient deprivation on immune function are measured in the mealworm beetle (Tenebrio molitor L.) reared in otherwise ideal conditions. The results suggest that immune effector system function is down-regulated during short-term nutritional deprivation, but is rapidly up-regulated to pre-deprivation levels after animals are allowed access to food. This rapid modulation of immune function in the context of nutritional status has important implications for measuring immune function in the field, as well as the interpretation of those measures.