To further dissect the composition of IgM-bound (IgM+) and non-IgM-bound (IgM−) gut bacteria, we randomly selected eight study participants (two control participants with NGT, three obese participants with IGT and three with type 2 diabetes) and flow-cytometrically sorted IgM+ and IgM− gut bacteria from their stool samples, followed by sequencing. Here, CD40LG is linked to type 2 diabetes mellitus.