Effects of rapid gravity load changes on immunophenotyping and leukocyte function of human peripheral blood after parabolic flight

One of the biological systems that suffers a physiological de-conditioning in space is the immune system. It is in charge of defending the body against pathogens and other aggressions. The aim of this work was to assess if there are any relevant changes in the aggregation of erythrocytes, cell count, immunophenotyping and functionality after parabolic flight. This effect has been assessed ex vivo using human peripheral blood, which was drawn from the radial vein (n = 6 healthy volunteers) and anticoagulated with heparin and EDTA. Blood samples were split into two aliquots and maintained in two identical thermally isolated boxes; one stayed on the ground whereas the other one was subjected to parabolic flight. The parabolic flight consisted of 15 parabolas performed with a Mudry CAP-10B acrobatic aircraft. Each parabola consists of 8 s of hypogravity preceded and followed by 2 s of hypergravity. Any of the biological parameters measured showed no statistically significant differences, with the exception of monocyte counting. Altered gravity could increase aggregation of red blood cells, as demonstrated by a decrease in the number of single cells after parabolic flight exposure. No counting changes in haemoglobin concentration were observed when comparing the two different groups. Furthermore, potential functional alterations of monocytes and neutrophils cannot be rejected. Although these possible changes could be associated with hypogravity, other factors such as hypergravity and acceleration or deceleration cannot be ruled out. Our findings indicate that, under this specific experimental setup, there was no significant alteration in leukocyte immunophenotyping and functional capacity when using ex vivo blood samples and short exposure to altered gravity.This study was partially supported by Thermo Fisher Scientific and Sysmex. We thank the CERCA Programme by Generalitat de Catalunya and the Germans Trias i Pujol Research Foundation for institutional support. We also acknowledge financial support from “Obra Social la Caixa”. This work has been also supported by positive discussion through the Agency for Management of University and Research Grants (AGAUR, Generalitat de Catalunya), Catalan Research Group (SGR) 2021 SGR 00002.Peer reviewe