Cytokines are small proteins that cells release to communicate. They regulate inflammation, immune response, and tissue repair. The I4 study measured 18 cytokines/chemokines at each timepoint: TNF-alpha, IL-8, IL-1ra, VEGF, CCL2, CCL4, CXCL5, thrombopoietin, and others.
Reading this chart
Y-axis shows relative cytokine concentration (normalized to pre-flight = 1.0). The 3-4x spike during flight means acute inflammatory signaling. TNF-alpha and IL-8 drove most of this. Recovery to baseline by R+45 shows the response was temporary.
Elevated pro-inflammatory cytokines (TNF-alpha, IL-8) mean the body is mounting an immune response. Anti-inflammatory cytokines (IL-1ra) rising simultaneously suggests the body is trying to regulate itself. This is the most intuitive biomarker set — 'high = stressed.'
Direct concentration values in pg/mL. Easy to z-score: (value - preflight_mean) / preflight_SD. Aggregate multiple cytokines into an 'Inflammation Index' by averaging their z-scores.
All AP-level math. No differential equations, no ML required. With n=4, descriptive statistics are more honest than hypothesis testing.
18 cytokines significantly altered during spaceflight
TNF-alpha and IL-8 spiked in-flight (acute inflammation)
VEGF elevated (vascular stress response)
Most cytokines returned to baseline by R+45 days
Perfect for the Inflammation domain score. Group pro-inflammatory vs anti-inflammatory cytokines, compute composite z-scores per crew member. Visual: radar chart showing cytokine profiles across timepoints.