CXCR5 and obesity due to melanocortin 4 receptor deficiency: To further interrogate how functional differentiation pathways are affected by obesity and bariatric surgery, we next assessed CXCR5+CD11c-IgD-CD27- DN1 and CD11c+CXCR5-IgD-CD27- DN2 B cell subset as well as CD27+CD38++ plasmablast frequencies.