Fig 2: Surface Plasmon Resonance Sensogram.(A) Binding of hSTC1 to immobilized IGF2R and regeneration of the CM5 sensor. hSTC1 was prepared at 5 μg/ml in the running buffer (PBS + 0.005% Tween 20) and was injected at 30 μl/minute and showed a large binding response. Following successive Pierce Gentle Ag/Ab Elution Buffer injections, all bound ligands were removed to baseline. (B) Reproducibility of hSTC1 binding. Three replicates of STC1 were prepared in the running buffer. The injection of hSTC1 was followed by dissociation and regeneration. A buffer blank (no binding response) was injected before and after hSTC1 binding cycles.

Fig 3: IGF2R-silencing on STC1 inhibited IL-1β secretion.(A) The effect of siRNA-silencing on the mRNA and protein expression of IGF2R. (B) The effects of hSTC1 (0.25 and 0.5 μg/ml) on IL-1β secretion in siRNACtrl and siRNAIGF2R-silencing cells. A significant reduction of secreted IL-1β was measured in hSTC1 treatment (0.5 μg/ml, *P < 0.001) as compared with the control. The inhibitory effect on IL-1β secretion was abolished in siRNAIGF2R transfection.Source data are available for this figure.

Fig 4: An immune signature composite well separates two SSIS groups.a Unsupervised hierarchical clustering of the Spearman correlation matrix of 5 immune cell clusters, 6 gene sets, 10 genes, 7 cytokines and 2 clinical parameters for the four SARS-CoV-2pos groups. b Circos plot visualizing the Spearman correlation matrix of 5 immune cell clusters, 6 gene sets, 10 genes, 7 cytokines and 2 clinical parameters for the four SARS-CoV-2pos groups. Each line represents a significant correlation with P < 0.05. Lines indicate positive (red) or negative (red) correlations. Size of nodes indicates degree centrality, with larger nodes representing higher degree. c PCA of the 4 immune cell clusters (T04, M02, M03 and M04), 2 gene sets (innate immunity: macrophage infiltration; GO: osteoclast differentiation), 5 genes (FAM110B, PAK3, PPP1R17, UTS2 and CCR5), and 1 cytokine (STC1) for the asymptomatic and presymptomatic subjects. Each dot represents a subject, colored by disease status. d Concentration of plasma MMP-1 and STC1 measured by ELISA in the asymptomatic and presymptomatic subjects of the Cohort 1. e Heatmap depicting the expression of MMP-1 and STC1 measured by ELISA in the asymptomatic and presymptomatic subjects of the Cohort 1. f PCA of the expression of MMP-1 and STC1 measured by ELISA in the asymptomatic and presymptomatic subjects of the Cohort 1. Each dot represents a subject, colored by disease status. g Concentration of plasma MMP-1 and STC1 measured by ELISA in the asymptomatic and presymptomatic subjects of the Cohort 2. h Heatmap depicting the expression of MMP-1 and STC1 measured by ELISA in the asymptomatic and presymptomatic subjects of the Cohort 2. i PCA of the expression of MMP-1 and STC1 measured by ELISA in the asymptomatic and presymptomatic subjects of the Cohort 2. Each dot represents a subject, colored by disease status. Significance in d, g was determined by unpaired Wilcoxon test. *P < 0.05.

Fig 5: hIGF2R binds to immobilized hSTC1.(A) STC1 Immobilization. CM5 sensor docked, primed with PBS + 0.005% Tween 20, and pre-cleaned with 50 mM NaOH for 30 s. Immediately before use, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC, 400 mM), and N-hydroxysuccinimide (NHS, 100 mM) were mixed and injected onto a flow cell for 7 min to activate the surface. hSTC-1 (20 μg/ml) in 10 mM sodium acetate buffer, pH 5.0, was injected for 7 min. Ethanolamine (1 M, pH 8.5) was injected for 7 min to de-activate/cap all unreacted EDC-NHS groups. A total of 6,250 RUs of STC-1 were immobilized. (B) IGF-R Binding and Regeneration. A solution of 2.5 μg/ml IGF2R in running buffer (PBS + 0.005% Tween 20) was injected for 5 min at 10 μl/minute to give a binding response of ∼120 RUs. With successive 15 and 30 s injections of Pierce Gentle Ag/Ab Elution Buffer, all bound ligand was cumulatively removed back to baseline—30-s injection was found to be the optimal time for regeneration.