Figure 4. Plasma from individuals with PASC induces NF-κB signaling, which is dampened by the spleen tyrosine kinase inhibitor piceatannol.

(A) A schematic of the Dectin-1 receptor reporter cell line. This cell line stably expresses the Dectin-1 receptor and an NF-κB reporter linked to SEAP so that Dectin-1 receptor stimulation by β-glucan can be measured by quantifying SEAP activity. Syk, spleen tyrosine kinase. (B) The Dectin-1 receptor reporter cells were treated with plasma from individuals with PASC or SARS-CoV-2–negative controls in the presence or absence of the Syk inhibitor piceatannol. NF-κB signaling was detected (OD_{620 nm}) 24 hours later. The comparison between the SARS-CoV-2–negative controls and PASC samples without piceatannol was performed using Mann-Whitney U test, and the comparisons between the conditions with and without piceatannol were performed using Wilcoxon’s signed rank tests. (C) Spearman’s rank correlation between levels of β-glucan in the plasma during PASC and NF-κB signaling induced by PASC plasma, using the Dectin-1 receptor reporter system.