CD27 and obesity due to melanocortin 4 receptor deficiency: While we found that obesity-associated reduction in CD24intCD38int memory B cells and expansion of IgD+CD27- naïve B cells was reversed post-bariatric surgery, CD11c+CXCR5-IgD-CD27- DN2 B cells and CD27+CD38++ plasmablasts associated with chronic inflammatory activation were expanded in post-bariatric patients compared to lean controls.