Although we did not observe any difference in the frequency of the IgD-CD27- DN B cells between lean individuals and pre-bariatric surgery patients with obesity, we did find a marked increase in the frequency of inflammatory CD11c+CXCR5-IgD-CD27- DN2 B cells and CD27+CD38++ plasmablasts post-bariatric surgery. This evidence concerns the gene CD27 and obesity due to melanocortin 4 receptor deficiency.