['Fatty acid composition of rodent diets can affect baseline immune function as measured in vitro and in vivo. Stress, in a variety of forms, can also affect immune function. Possible interaction between diet and other stressors has not been fully explored. We examined the interaction between sleep deprivation stress and dietary fatty acid composition in altering lymphocyte responses to mitogen stimulation.', 'Rats were fed diets containing various sources of fatty acids, then were subjected to sleep deprivation. Splenocytes were harvested and assayed for responsiveness to various mitogens, using a 72-h proliferation assay.', 'Rats subjected to sleep deprivation experienced significant suppression of in vitro proliferative response to various mitogens. This immune suppression was dependent on duration of sleep deprivation. Feeding sleep deprived rats a diet enriched in fatty acids abrogated the effect of sleep deprivation.'] Does increased dietary fat prevent sleep deprivation-induced immune suppression in rats?