IgG targeting of the fecal microbiota. The percentage of IgG-positive (%IgG+) fecal bacteria by flow cytometry relative to an isotype control and a total IgG concentration (ng/g wet weight); b country of origin and c stunting status. N = 75. Significance was determined by Spearman’s correlation (a) and Wilcox rank sum test (b, c). Red datapoints in b and c indicate the five children selected for IgG-SEQ analysis. d Top IgG-targeted taxa in five children with high IgG-coating of the fecal microbiota. Color saturation reflects the numerical IgG Index (red = positively targeted, blue = negatively targeted). The top 10 most and least-targeted taxa in each child were selected to display in the heatmap.