A microbiota enriched in SCFA-producing bacteria sustain IL-10 production by iNKT cells. [A] IL10 protein concentration in the supernatants of mucosal iNKT cells co-cultured with moDCs and mucosa-associated microbiota isolated from healthy donors [n = 6] or CD patients [n = 6]. Left panel, single donors plot representation. Right panel, cumulative plot representation. [B] Frequency of IL10-producing iNKT cells upon co-culture with moDC exposed to healthy- or CD-derived mucosa-associated microbiota. [C] PCoA of beta-diversity of mucosa-associated microbiota as measured by Unweighted UniFrac distance [right] and alpha-diversity as measured by Shannon entropy index [left]; **p <0.01. [D] Volcano plot representing the significantly enriched bacterial taxa [FDR p <0.05] in NKT10-high vs -low patients by the DEseq2 analysis. The names of the significantly enriched ASVs described as SCFA-producing bacteria and classified to the genus are reported. [E] Heatmap of Spearman’s rho correlations between the significantly enriched SCFA-producing bacteria in iNKT10-high and -low patients with the indicated cell populations, clinical and gene expression data. The significant correlations with p-value <0.05 are indicated with an asterisk [*]. FC, faecal calprotectin; CRP, C-reactive protein. [F] Cytokines production by iNKT cells upon co-culture with moDC and mucosa-associated microbiota derived from iNKT10-high or -low patients; *p ≤0.05, **p ≤0.01, ***p ≤0.001, Mann-Whitney U test. G] Histological and endoscopic analyses at the beginning of the enrolment [T0] and 54 weeks post-enrolment [T54] in iNKT10-high and -low CD patients. [H] % of CD patients classified as inflamed [with a cumulative score ≥2 calculated summing 1 point with CRP >0.5 mg/dl, 1 point with FC >50 ug/g and 1 point for evident signs of inflammation/tissue damage], levels of faecal calprotectin and serum C-reactive protein 54 weeks post-enrolment; exact p-values for Fisher’s exact test [% inflamed] and Mann-Whitney test [FC and CRP] are shown. ASV, amplicon sequence variant; SCFA, short chain fatty acid; FDR, false-discovery rate; PCoA, principal coordinate analysis; moDC, monocyte-derived dendritic cells.