Overweight and obese adult humans have a defective cellular immune response to pandemic H1N1 influenza A virus

OBJECTIVE: Obese adults have a greater risk of morbidity and mortality from infection with pandemic H1N1 influenza A virus (pH1N1). The objective of the present study was to elucidate the specific mechanisms by which obesity and overweight impact the cellular immune response to pH1N1. DESIGN AND METHODS: We stimulated peripheral blood mononuclear cells from healthy weight, overweight, and obese individuals ex vivo with live pH1N1 and then measured markers of activation and function using flow cytometry and cytokine secretion using cytometric bead array assays. RESULTS: Our data indicate that CD4(+) and CD8(+) T cells from overweight and obese individuals expressed lower levels of CD69, CD28, CD40 ligand, and interleukin-12 receptor, as well as, produced lower levels of interferon-γ and granzyme B, compared to healthy weight individuals, suggesting deficiencies in activation and function. Dendritic cells from the three groups expressed similar levels of major histocompatibility complex-II, CD40, CD80, and CD86, as well as, produced similar levels of interleukin-12. CONCLUSIONS: The defects in CD4(+) and CD8(+) T cells may contribute to the increased morbidity and mortality from pH1N1 in obese individuals. These data also provide evidence that both overweight and obesity cause impairments in immune function.