Aim: 

In order to determine in space the ability of T lymphocytes to interact with antigen-presenting cells, we focused on the dynamic membrane-cytoskeletal interactions in modelled microgravity.

Cellular control of these adhesive connections requires the integrin cytoplasmic tails activation of LFA-1 by binding to intracellular ligands. Recent findings indicate that talin, a major cytoskeletal actin-binding protein, that binds to integrin b tails and colocalizes with activated integrins, plays a critical role in both activating integrin and providing a cytoskeletal link.

Methods: 

Antibody induced LFA-1 capping of in vitro T cell surfaces was performed and cytoskeletal proteins, talin and vinculin, were detected, by double immunofluorescence microscopic labelling, after PMA treatment and exposure to modelled microgravity conditions, using Random Positioning Machine (RPM). We also investigated talin and vinculin expression by immunoblotting.

Results: 

Our results indicate that there was no significant association of either talin or vinculin with LFA-1 integrin in resting T lymphocytes, but upon PMA stimulation for 45 min and 18 h, a specific interaction and colocalization arose between LFA-1 and talin, not involving vinculin in ground controls; in contrast, in RPM low g, no capping therefore no colocalization were visualized after 45 min, but a linkage between LFA-1 and talin was observed after 18 h. Immunoblotting assay revealed no significant difference on talin and vinculin expression, between low g and 1 × g samples after 18 h, whereas mostly talin expression appeared significantly decreased after exposition to RPM for 45 min.

Conclusion: 

The delayed talin- to- LFA-1 integrin linkage observed in RPM microgravity indicate a delayed membrane-cytoskeletal association. This impairment, in addition to previous cytoskeletal structures alterations, might be responsible for the reduced T cell mitogenic activation and monocyte -T cell interactions observed in space.

The research was supported by Italian Space Agency (ASI)