Effect of microgravity modeling on interferon and interleukin responses in the rat.

Rats were placed in whole-body harness suspension in three configurations: antiorthostatic hypokinetic/hypodynamic suspension (AAH) to induce headward body fluid redistribution and unload the limbs, orthostatic hypokinetic/hypodynamic suspension (OHH) to unload the limbs without fluid redistribution, and harness restraint (HR) to produce the restraint stress of the model without fluid redistribution or musculoskeletal disuse. AHH and OHH suspension transiently increased interferon-gamma (IFN-gamma) production in response to the mitogen concanavalin A. Harness restraint alone did not affect IFN-gamma response. However, both suspension modeling and harness restraint caused a transient reduction in interleukin-1 (IL-1) and IL-2 responses to mitogen. This suggests that factors associated with musculoskeletal unloading affected IFN-gamma responses, while IL-1 and IL-2 responses were affected by the physiological stress of restraint.