Effects of deceleration on the humoral antibody response in rats.

The purpose of this experiment was to determine the effects of hyper-gravity (hyper-G) followed by a return to normal gravity (deceleration) on the immune system of rats. Hyper-G was simulated by chronic centrifugation. Eighteen 35-d-old male rats were divided into three groups of six rats each. Two groups were exposed to 2.1 G and 3.1 G, respectively, for 28 d. The third group served as 1.0 G controls. Rats were removed from the centrifuge on day 29. All rats were immunized with sheep red blood cells (SRBC) on days 29, 42, and 57; rats were bled on days 36, 47, and 62. Hematocrits and anti-SRBC titers were determined each day the rats were bled. White blood cell (WBC) counts were determined on day 47. On day 63, all rats were sacrificed and organ:body mass ratios obtained for a number of organs. Centrifuged rats ate and gained significantly less. The organ:body mass ratios for the adrenal glands, kidneys, lungs, heart, and thymus were unaffected by deceleration. Although marginally significant (p less than 0.05) decreased organ:body mass ratios were found for the liver and spleen in the 3.1 G group, this effect may not be real, due to the small number of rats used. No significant differences were found in hematocrits, WBC counts, or anti-SRBC titers. These experiments indicate that deceleration does not adversely affect these particular aspects of the immune system. However, they do not preclude the possibility that other aspects of the immune system, such as interferon or complement, may be affected.