[Lymphoid organs of monkeys in head-down-tilt hypokinesia (an experimental morphological study)]

The histological study of the thymus, spleen and inguinal lymph nodes of monkeys exposed to head-down tilt (-6 degrees) for 7 or 19 days showed that the exposure caused an acute stress that resulted in the thymus involution and hypoplasia of the lymphoid tissue of the spleen and lymph nodes. The exposure produced fluid redistribution due to which the spleen blood content decreased and the mass of inguinal lymph nodes increased. This was induced by partial pooling of the lymph flowing from the lower extremities. The exposure also led to autoimmune developments.