Fig. 5: Lack of overaction of NLRP3 inflammation activation in MIS-C and increased active caspase 8 activity in MIS-C monocytes.

Whole blood samples from children with MIS-C (n = 14), acute COVID-19 pneumonia (COVID-19, n = 15), other paediatric admissions (Paediatric Admission, n = 16) and MIS-C follow-up patients (MIS-C_Follow, collected about 1 month post hospital discharge, n = 6) were stimulated in vitro with LPS (50 ng/ml), ATP (5 mM), or LPS plus ATP (50 ng/ml and 5 mM respectively, ATP was added 3 h after the LPS addition). Cytokines were measured 4 h and 24 h after stimulation. Levels of IL-1β, IL-18 and TNF-α levels were shown in (A–C). The lower limit of quantification of IL-1β is about 18 pg/ml, 16.5 pg/ml for IL-18 and 7.3 pg/ml for TNF-α (grey-shaded areas). In the MIS-C group, samples with glucocorticoids/IVIG treatment in the last 24 h before sampling were marked as unfilled circle. Horizontal line and error bars show the mean and standard deviation. Results of two-way ANOVA with post hoc Tukey’s multiple comparisons test between the first 3 groups (all collected at the acute stage) within each treatment condition are shown. There were no significant differences between the MIS-C-Follow and paediatric admission group by multiple Mann–Whitney tests with each treatment condition. D Monocyte active caspase staining signals from 5 MIS-C and 6 COVID-19 blood monocyte samples. Left: histograms of active caspase 8 staining (red lines indicate MIS-C, blue COVID-19). Right: Quantification of active caspase 8 median fluorescence intensity. Mann–Whitney test was used to compare the 2 groups. Source data are provided as a Source Data file.