Across all soluble proinflammatory markers we examined, 6 showed a statistically significant positive correlation between cytokine or epithelial marker and antibody quantity regardless of COVID-19 disease severity (Figure 4), including ICAM (r = 0.507, P < 0.001), IL-1β (r = 0.172, P = 0.0233), IL-4 (r = 0.304, P < 0.001), IL-6 (r = 0.21, P= 0.037), TNFα (r = 0.335, P< 0.001), and Syndecan (r = 0.613, P < 0.001). Here, SDC1 is linked to COVID-19.