The Lymphocyte Story – an Overview of Selected Highlights on the in Vitro Activation of Human Lymphocytes in Space

Abstract

Since the first flight of humans into space it is known that space flight affects the immune system; especially a weakening of the reactivity of T-lymphocytes after flight has been observed. In an in vitro experiment, proposed by Augusto Cogoli and flown in Spacelab-1 in 1983, the activation of T-lymphocytes was found to be strongly inhibited in microgravity. This surprising result triggered extended investigations in space and on the ground by us and other research teams. T-cells are that subpopulation of lymphocytes responsible for the activation of the specific immune system. The mechanism of T-cell activation is very complex; 3 different signals are required as well as an interaction between T-lymphocytes and monocytes. Cell motility based on a continuous rearrangement of the cytoskeletal network within the cell is essential for cell-cell contacts. The objective of all our experiments performed on different platforms in space as well as in simulated microgravity on ground was to understand and explain the dysfunction of the cell activation under reduced gravity conditions. On sounding rockets we have studied the influence of microgravity on the delivery of the first signal, the motility of lymphocytes as well as changes in the cytoskeletal structure and early gene expression. On long term missions we investigated many aspects of the delivery of the 2 nd and 3 rd signal, including motility and aggregate formation of lymphocytes, interaction of lymphocytes with monocytes, motility of monocytes and changes in different cytoskeletal structures.