Housing environment alters delayed-type hypersensitivity and corticosterone concentrations of individually housed male C57BL/6 mice

Housing conditions can alter both the physiology and behaviour of laboratory animals. Forced-air-ventilated micro-isolation systems increase the efficient use of space, decrease the incidence of disease among laboratory rodents, and provide better working conditions for animal care staff, however, such systems can increase breeding variability and mortality. We examined the possibility that stressors associated with automated housing conditions evoke subtle changes among immune, endocrine, and behavioural parameters in mice housed in a static versus a forced-air-ventilated micro-isolation system. In addition, we assessed the effects of housing in the forced-air-ventilated micro-isolation system both with and without the use of an automatic watering system. Housing in the forced-air-ventilated micro-isolation system, using the automatic watering system, suppressed delayed-type hypersensitivity (DTH) responses, a measure of cell mediated immune function, compared with the responses of mice housed in static cages. Hypothalamic-pituitary-adrenal axis function was also altered by housing in the forced-air-ventilated micro-isolation system with the use of the automatic watering system, such that mice in this housing system had lower resting corticosterone concentrations and increased reactivity to restraint. Despite these changes in corticosterone, housing condition did not alter activity level or exploratory, anxiety-like, or depressive-like behaviours. These results suggest that investigators should carefully consider housing conditions in studies of immune and endocrine function.