ABSTRACT
The effect of spaceflight on lymphocytes of the peripheral blood was investigated in the Austrian cosmonaut flying the Austro-Soviet mission Austromir. Blood was sampled before and after flight, and the following parameters studied: quantities of lymphocytic subsets (T cells, helper cells, suppressor cells, B cells and natural killer cells); mitogenic stimulation of lymphocytes--DNA (= deoxyribonucleic acid) synthesis and expression of Interleukin-2-receptor; structural modification of DNA, unscheduled DNA synthesis and sister chromatid exchanges. Besides reducing the number of natural killer cells, spaceflight caused on impairment of lymphocyte activity and a slight modification of DNA structure. 4 weeks after flight, control values were reestablished, indicating efficient repair mechanisms.