C004

Scores reflect how far this individual moved from their own pre-mission baseline. All thresholds are individual-relative unless labeled otherwise.

Immune & Inflammatory Response

How the body's defense system shifts during spaceflight

Mission-Wide Signal · n=4 crew members

The immune system showed the largest and most directionally consistent suppression of any biological category measured — 76.9% of immune genes downregulated post-flight across all four crew members. Three mechanisms converge: cortisol-mediated lymphocyte shutdown from anticipatory pre-launch stress, radiation-induced loss of radiosensitive immune cells in orbit, and microgravity-driven cytoskeletal disruption that physically prevents T-cell activation.

B-Cell Signaling

↓ suppressed

CD79B (−1.5×) — the signaling engine of the B-cell receptor — is the single largest fold-change in the entire dataset. IGKC (−1.329×) reduces the building blocks of antibodies themselves. The combined effect is a measurable attenuation of the body's antibody-based immune response.

CD79B −1.5× · IGKC −1.329×

Innate Antiviral Defense

↓ suppressed

IFNAR2 (−1.128×) is the receptor that signals the body to mount a response to viral threats. IFIH1/MDA5 (−0.950×) is the intracellular sensor that detects viral RNA inside cells. Both are suppressed — the body's early-warning system for viral infection is quieted.

IFNAR2 −1.128× · IFIH1/MDA5 −0.950×

T-Cell Activation

↓ suppressed

TAGAP (−0.889×) organizes the cytoskeletal machinery T-cells need to form the tight cell-to-cell contact (immune synapse) required to activate each other. In microgravity the cytoskeleton reorganizes differently, and cells may be physically unable to complete this activation step — a mechanism that would amplify over longer missions.

TAGAP −0.889×

Stress Hormone–Immune Axis

↓ suppressed

FKBP4 (−0.896×) is required for the glucocorticoid receptor to function. Sustained cortisol elevation from pre-launch anticipatory stress mechanistically shuts down lymphocyte activation and B-cell proliferation — contributing to the immune suppression pattern even before launch.

FKBP4 −0.896×

Pre-Launch Leukocyte Surge

↑ elevated

WBC +33%, Lymphocytes +56%, Neutrophils +27% at L-3 — a classic anticipatory stress response. The surge is physiologically expected before a major physical stressor and returned to baseline post-flight. The Lymphocyte peak (+56%) is the largest pre-launch response of any cell type measured.

WBC +33% · Lymphocytes +56% · Neutrophils +27% at L-3

Post-Flight Monocyte Elevation

↑ elevated

Monocytes rose +30% at L-3 in proportion to the overall WBC surge but, unlike other cell types, remained +22% above individual baseline at R+1. Elevated monocytes at this stage are associated with sustained inflammation, ongoing tissue repair signaling, or immune remodeling after physiological stress.

+22% above baseline persists at R+1

Regulatory Mechanism

m6A RNA methylation increased 51 times during spaceflight versus only 2 decreases — acting as a system-wide speed limiter on gene translation. When immune gene expression rises under stress, m6A tags the resulting mRNA strands for accelerated degradation by YTHDF2 protein. The body attempts to increase immune gene output, but the message is destroyed before protein accumulates, creating a self-reinforcing suppression loop under sustained stress.

Source: OSD-569/571 bulk RNA-seq · OSD-575 cytokine panel · CBC longitudinal draws · n=4 crew members