Human Obesity Reduces the Number of Hepatic Leptin Receptor (Ob-R) Expressing NK Cells

OBJECTIVE: In the industrialized world, obesity is an increasing socioeconomic health problem. Obese subjects have a higher risk of developing several types of cancer. NK cells are an integral component of the innate immune system, able to destruct tumor cells. The adipokine leptin plays a crucial role in the development of obesity and its related diseases. Peripheral leptin signaling is modulated by the liver. METHODS: The aim of this study was to evaluate the number of hepatic NK cells (CD56+) and the number of leptin-receptor positive (Ob-R+) cells in the livers of five normal-weight and five obese humans. Livers were removed during autopsy and accurately defined sections were stained immunohistochemically and CD56+, Ob-R+, and double-positive cells were quantified. RESULTS: Results revealed a dramatic reduction of NK cells and Ob-R-expressing NK cells in the livers of obese individuals. CONCLUSIONS: The present study demonstrates, for the first time, body-weight-dependent numbers of hepatic NK cells. This supports the hypothesis of obesity-associated alterations of immune cell numbers in different human organs.