Beyond Earth: How Space Travel Affects the Immune System

By Abhijeet Kulkarni.

More likely than not, most of us have dreamt of being an astronaut exploring moons, planets, and galaxies in fancy spaceships as children. We have looked up to sky at night and wondered if a twinkling star is a visiting spaceship. It is possible, right? Exploring space and space flight is not only a major topic of discussion in today’s world but it could be a real possibility in the not-so-distant future. Considering the pace of technological advancements, visiting other planets in the coming decades doesn’t seem farfetched. For example, in October 2024, SpaceX was able to “grab” their super heavy booster at the launch site, which facilitates quick redeployment for the future [1], on its first attempt! A must-watch if you haven’t seen the video [1, 2]. Based on available media, exploring space seems to be visually stunning, breathtaking and extraordinary making us want to visit it. However, as expected, space travel can greatly affect different systems of the human body including the circulatory, neurological, musculoskeletal and immune systems among others [3, 4].

Space flight is accompanied by several stressors including radiation, microgravity, changes in sleep patterns, psychological stress, nutrient deficiencies and oxidative stress [5]. As mentioned, these stressors, separately and in combination can greatly affect systems of the human body. The immune system is reported to be among the most affected during space flight [3]. Dysregulations in the immune system have been reported in 6-month orbital space flights [6]. Diseases such as upper respiratory tract infections, conjunctivitis, influenza, viral gastroenteritis, and allergic reactions have been documented [3, 7]. Specifically, dysregulations of the immune system are coupled with reactivation and shedding of latent herpesviruses [6, 7]. It is particularly interesting how both, infections due to ineffective and inflammatory conditions due to overactive immune cells have been observed. Based on these and additional observations [6], it has been hypothesized that space flight is associated with a shift towards a Th2 response [6].

Generally, cells can sense changes in gravity and induce intracellular signalling altering cell morphology and function which can lead to systemic changes [3]. Among different cell types, immune cells are greatly impacted by microgravity [3]. Microgravity has been reported to limit lymphocyte activation, migration, proliferation, and function [3]. Additionally, reduced frequency of monocytes, reduced activation and polarization of macrophages, impaired functioning of dendritic cells and limited functioning of neutrophils have also been reported [3]. It is critical to note that such observations are often based on experiments conducted in simulated microgravity and the method of inducing microgravity can influence the observations. For example, contradictory observations such as decrease and increase in dendritic cells have been reported and the use of different methodologies to induce microgravity has been implicated for the discrepancy [3]. The use of simulated environments greatly facilitate research but also possess their limitations [6]. Nonetheless, these experimental approaches are essential in not only predicting and understanding possible dysregulations but also for the development of counter measures which can be employed to limit detrimental effects due to these dysregulations. Counter measures based on our current understanding are already in place and being employed on the ISS [6]. These range from medical screening and vaccinations to radiation shielding and optimization of exercise equipment and nutrition [6]. Several additional measures are currently being evaluated for their utility [6]. In their review, Crucian et al. describe several such measures and the reasoning for employing the same [6]. Similarly, Lv et al., report in excellent detail the effects of microgravity on the cells of the immune system and potential counter measures which can be helpful in limiting microgravity induced immune system dysregulations during space flight [3].

In summary, the immune system is greatly affected by space flight and further research is required to better understand these dysregulations and prepare for them. Fortunately, advancements in technology not only enable such studies in space but also in simulated environments. Such studies have been crucial in improving our understanding of the effects of space stressors on the human body. This short article provides a miniscule overview of the literature available from decades of research to pique your interest. Hopefully it did! Do check out the references for more. Cheers!

On a separate note, we at the SYIS are looking for guest writers for this blog! We are largely interested in articles with an immunological perspective.
Interested? Please reach out to us here.

References:

1. Stallard, E. (2024, October 13). Elon Musk’s Starship booster captured in world first. https://www.bbc.com/news/articles/c8xe7exjy1go
2. BBC (2024, October 13). Watch astonishing moment Starship booster caught in mid-air ‘chopsticks manoeuvre’. https://www.bbc.com/news/videos/cly57d5jw7eo
3. Lv H, Yang H, Jiang C, Shi J, Chen RA, Huang Q, Shao D. Microgravity and immune cells. J R Soc Interface. 2023 Feb;20(199):20220869. doi: 10.1098/rsif.2022.0869. Epub 2023 Feb 15. PMID: 36789512; PMCID: PMC9929508.
4. Garrett-Bakelman FE, Darshi M, Green SJ, Gur RC, Lin L, Macias BR, McKenna MJ, Meydan C, Mishra T, Nasrini J, Piening BD, Rizzardi LF, Sharma K, Siamwala JH, Taylor L, Vitaterna MH, Afkarian M, Afshinnekoo E, Ahadi S, Ambati A, Arya M, Bezdan D, Callahan CM, Chen S, Choi AMK, Chlipala GE, Contrepois K, Covington M, Crucian BE, De Vivo I, Dinges DF, Ebert DJ, Feinberg JI, Gandara JA, George KA, Goutsias J, Grills GS, Hargens AR, Heer M, Hillary RP, Hoofnagle AN, Hook VYH, Jenkinson G, Jiang P, Keshavarzian A, Laurie SS, Lee-McMullen B, Lumpkins SB, MacKay M, Maienschein-Cline MG, Melnick AM, Moore TM, Nakahira K, Patel HH, Pietrzyk R, Rao V, Saito R, Salins DN, Schilling JM, Sears DD, Sheridan CK, Stenger MB, Tryggvadottir R, Urban AE, Vaisar T, Van Espen B, Zhang J, Ziegler MG, Zwart SR, Charles JB, Kundrot CE, Scott GBI, Bailey SM, Basner M, Feinberg AP, Lee SMC, Mason CE, Mignot E, Rana BK, Smith SM, Snyder MP, Turek FW. The NASA Twins Study: A multidimensional analysis of a year-long human spaceflight. Science. 2019 Apr 12;364(6436):eaau8650. doi: 10.1126/science.aau8650. PMID: 30975860; PMCID: PMC7580864.
5. Tocci D, Ducai T, Stoute CAB, Hopkins G, Sabbir MG, Beheshti A, Albensi BC. “Monitoring inflammatory, immune system mediators, and mitochondrial changes related to brain metabolism during space flight”. Front Immunol. 2024 Oct 1;15:1422864. doi: 10.3389/fimmu.2024.1422864. PMID: 39411717; PMCID: PMC11473291.
6. Crucian BE, Choukèr A, Simpson RJ, Mehta S, Marshall G, Smith SM, Zwart SR, Heer M, Ponomarev S, Whitmire A, Frippiat JP, Douglas GL, Lorenzi H, Buchheim JI, Makedonas G, Ginsburg GS, Ott CM, Pierson DL, Krieger SS, Baecker N, Sams C. Immune System Dysregulation During Spaceflight: Potential Countermeasures for Deep Space Exploration Missions. Front Immunol. 2018 Jun 28;9:1437. doi: 10.3389/fimmu.2018.01437. PMID: 30018614; PMCID: PMC6038331.
7. Crucian BE, Makedonas G, Sams CF, Pierson DL, Simpson R, Stowe RP, Smith SM, Zwart SR, Krieger SS, Rooney B, Douglas G, Downs M, Nelman-Gonzalez M, Williams TJ, Mehta S. Countermeasures-based Improvements in Stress, Immune System Dysregulation and Latent Herpesvirus Reactivation onboard the International Space Station – Relevance for Deep Space Missions and Terrestrial Medicine. Neurosci Biobehav Rev. 2020 Aug;115:68-76. doi: 10.1016/j.neubiorev.2020.05.007. Epub 2020 May 25. PMID: 32464118.

Illustration icons: Flaticon, Servier Medical Art, Adobe Stock.