Context: Obesity-related chronic inflammation is implicated in the pathogenesis of type 2 diabetes (T2D).

Objective: The objective of the study was to determine the effects of weight loss on immune cells in T2D and prediabetes.

Design and Setting: Thirteen obese subjects with T2D or prediabetes underwent 24 wk dietary energy restriction with gastric banding surgery at 12 wk.

Main Outcome Measures: Measures included weight, waist, and insulin resistance; surface activation marker expression on circulating immune cells; T-helper cell polarization: type 1 (Th1), type 2 (Th2); adipose tissue macrophage number and activation in sc and visceral adipose tissue.

Results: Mean total weight loss was 13.5%. There were significant decreases in expression of proinflammatory activation markers: granulocyte CD11b, monocyte CD66b, and T cell CD69 and CD25. Proinflammatory Th1 cell numbers fell by greater than 80%, as did the Th1 to Th2 ratio. The fall in Th1 to Th2 ratio related to weight (P < 0.05) and waist loss (P < 0.05). Reduction in immune cell activation was more pronounced in subjects with prediabetes. Weight and abdominal fat loss were predicted by lower activation of adipose tissue macrophage in sc and visceral adipose tissue (P < 0.05).

Conclusions: Energy restriction before and after gastric banding attenuates activation of circulating immune cells of the innate and adaptive immune system in T2D and prediabetes. The role of immune cells in the chronic inflammation of obesity and T2D requires further investigation.