T-bet+ B cells promote adipose tissue inflammation and metabolic disorder during obesity.

Abstract

Obesity is a public health crisis affecting a large and ever-growing portion of the global population. Obesity is associated with an increased risk of death and comorbidities, resulting in lower quality of life for obese patients and increased economic costs on healthcare systems. Obesity is linked with a low-grade and chronic inflammation in the adipose tissue, which further exacerbates metabolic dysfunctions. Understanding the mechanisms and immune cell types promoting this inflammation would allow for the development of new therapies to restore immune regulation in obese patients. Our lab has identified a subset of B lymphocytes which is expanded in the adipose tissue of humans and mice during obesity. This subset is characterized by the co-expression of T-bet and CD11c, production of IgG2c, and its expansion is dependent on the presence of iNKT cells. In vivo studies with mice fed a high fat diet reveal that these Tbet+ B cells promote inflammation. Serum transfer experiments and flow cytometry analysis revealed that this effect is mediated through the production of CXCL10 and antibodies. The absence of T-bet+ B cells does not appear to affect adipose CD4+ T cells or NK cells, but it reduces macrophage polarization towards a more proinflammatory phenotype. Transgenic mice engineered to lack T-bet+ B cells not only have reduced adipose tissue inflammation, but present improved metabolic function as well, gaining less weight on a high-fat diet than littermate controls and presenting improved glucose tolerance. Based on these results, T-bet+ B cells represent an interesting potential target to reduce inflammation in obese patients and improve their metabolic functions.