Natural killer cells after ALTAIR mission

Area of Science:

• Immunology
• Space Medicine
• Cellular Biology

Background:

• Reduced in vitro natural killer (NK) cytotoxic activity is a known consequence of both prolonged and short-term space flights.
• Understanding the specific effects of space travel on immune cell function is crucial for astronaut health.

Purpose of the Study:

• To investigate the impact of space flight on NK cell functions, counts, and the production of Interleukin-2 (IL-2) and Tumor Necrosis Factor (TNF) by lymphocytes.
• To assess immune responses in French and Russian cosmonauts after varying durations of space missions.

Main Methods:

• Analysis of NK cell cytotoxic activity, target cell binding and lysis capacity, and NK cell percentages.
• Measurement of IL-2 and TNF production by lymphocytes stimulated with specific agents (PMA, PHA).
• Immunological examinations of cosmonauts before and after space flight.

Main Results:

• A French cosmonaut showed decreased NK cell cytotoxic activity, target cell interaction, and NK cell percentage after a 21-day flight.
• This cosmonaut also exhibited a twofold reduction in TNF production stimulated by PMA and PHA/PMA, but not in 48-hour PHA-stimulated cultures.
• IL-2 biological activity remained unchanged, and no significant deviations were found in two Russian cosmonauts after a 197-day flight.

Conclusions:

• Space flight can lead to reduced NK cell cytotoxic activity and potentially fewer circulating effector cells.
• While some immune functions like TNF and IL-2 production may be resilient, others are demonstrably affected by space exposure.
• Further research is needed to fully elucidate the mechanisms behind space flight-induced immune alterations.