During intense activity, many insects use an exchangeable apolipoprotein, apolipophorin III, for lipid transport. However, under resting conditions, apolipophorin III acts as an immune surveillance molecule. My lab has found that intense activity (e.g. flight) in crickets (Gryllus texensis) leads to transient immunosuppression. For approximately one hour after flight, crickets are more susceptible to the Gram-negative bacterium Serratia marcescens. During flight, hemolymph lipid levels increase, and the apolipophorin III concentration decreases. Decreasing apolipophorin III levels by injecting adipokinetic hormone also leads to immunosuppression. Reducing the decrease in apolipophorin III during flight by preloading crickets with trehalose reduces flight-induced immunosuppression. Injections of purified apolipophorin III also reduced flight-induced immunosuppression. These results suggest that when apolipophorin III is ‘borrowed’ for lipid transport, immune surveillance declines, resulting in an increased susceptibility to bacterial infection.