Gene expression changes after exposure to acute heatstress and/or to bacteriallipopolysaccharide (LPS) were investigated by measuring globalgene expression in two immune organs,bursa and thymus,from two chicken lines, Fayoumi and broiler. Over 1,600genes had significant expression changes in response to treatment; greaternumberswere identified in bursa for Fayoumi and in thymus forbroilers. Heat stress suppressed gene expression responses to LPS in both tissues.Both Heat and LPS impacted expression of immune cell traffickinggenes; these pathwaysneed to be investigated for potential to improve immune responses in heat-stressed chickens.