Effect of hypogravity on human lymphocyte activation.

Cultures of human lymphocytes were exposed to the mitogen concanavalin A in a low-G environment generated by a fast rotating clinostat. DNA-synthesis was determined by incorporation of 3H-thymidine as the parameter for activation, cell ultrastructure was analyzed by electron microscopy, and cell movements were recorded by a cinecamera. The results were compared with 1-G controls. The cells cultured at low G show: (i) depression of activation by 50%, (ii) appearance of "mitochondria-rich" cells, and (iii) enhanced formation of pseudovilli and uropods. Our investigations in vitro at low and high G and reports on the effect of spaceflights on lymphocytes from cosmonauts and astronauts suggest that hypogravity depresses, whereas hypergravity enhances, lymphocyte activation by mitogens. This study is complementary to an experiment which will study the in vitro activation of lymphocytes in weightlessness during the first Spacelab mission.

Effect of gravity on lymphocyte proliferation.

Reports on postflight examination of lymphocytes from crew members of soviet and american spaceships show a depression of reactivity towards mitogens in vitro. The purpose of this communication is to present experimental evidence that gravity can interfere with lymphocyte activation. Lymphocytes were incubated in the presence of concanavalin A in a centrifuge at 2 and 4 g for four days. This environment causes a significant acceleration of the response to the mitogen. In addition, remarkable differences in the ultrastructure of cells grown at 1 g and 4 g are observed by electron microscopy. This investigation is related to the experiment "Effect of weightlessness on lymphocyte proliferation" experiment which will be performed during the first Spacelab mission.