B Lymphocytes in Human Subcutaneous Adipose Crown‐Like Structures

Accumulation of macrophages and T cells within crown‐like structures (CLS) in subcutaneous adipose tissue predicts disease severity in obesity‐related insulin resistance (OIR). Although rodent data suggest the B cell is an important feature of these lesions, B cells have not been described within the human CLS. In order to identify B cells in the human subcutaneous CLS (sCLS) in obese subjects and determine whether the presence of B cells predict insulin resistance, we examined archived samples of subcutaneous and omental fat from 32 obese men and women and related findings to clinical parameters. Using immunohistochemistry, we identified B (CD19 + ) and T cells (CD3 + ) within the sCLS and perivascular space. The presence and density of B cells (B cells per high‐power field (pHPF), T cells pHPF, and B cell:T cell (B:T) ratio) were compared with measures of insulin resistance (homeostasis model assessment (HOMA)) and other variables. In 16 of 32 subjects (50%) CD19 + B cells were localized within sCLS and were relatively more numerous than T cells. HOMA was not different between subjects with CD19 + vs. CD19 − sCLS (5.5 vs. 5.3, P = 0.88). After controlling for diabetes and glycemia (hemoglobin A 1c (HbA 1c )), the B:T ratio correlated with current metformin treatment ( r = 0.89, P = 0.001). These results indicate that in human OIR, B cells are an integral component of organized inflammation in subcutaneous fat, and defining their role will lead to a better understanding of OIR pathogenesis and potentially impact treatment.