Agnirva Space Premier League - Expedition #31032: Testing Immunity in Space: Delayed-Type Hypersensitivity Assay on the ISS

The immune system is like a fortress guarding the body, but how well does it hold up in space? To answer this, scientists are turning to a powerful tool known as the Delayed-Type Hypersensitivity (DTH) assay. This experiment, led by Dr. Alexander Choukèr and Dr. Judith-Irina Buchheim from the University of Munich, uses in vitro testing on the International Space Station (ISS) to measure cellular immunity during long missions.

In simple terms, the DTH assay tests how the immune system responds to familiar pathogens. Normally, when the body has encountered a virus or bacterium before, it reacts quickly and strongly upon re-exposure. This test simulates that reaction in a laboratory setting using astronauts’ immune cells.

Conducted across Expeditions 68 to 74, the experiment provides data on how spaceflight affects the body's ability to mount a memory immune response. This is crucial because astronauts in microgravity experience immune dysregulation—meaning their defenses can become weaker or behave unpredictably.

To perform the assay, blood samples are drawn from astronauts and cultured with known antigens (substances that trigger immune responses). Scientists then measure cytokine production and cell proliferation, which indicate immune memory and activation.

Results so far show that microgravity may reduce immune cell responsiveness. That means the body’s ability to “remember” past infections could be compromised, increasing risk during long-duration missions. This highlights the need for robust pre-mission health monitoring and in-mission support for immune health.

The insights gained also have applications on Earth, especially in monitoring immune responses in aging populations, immunocompromised patients, and people undergoing stress-related immune suppression.

This experiment showcases how space can serve as a testbed for medical innovation, offering new ways to understand and protect human health in extreme environments.

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