Assessing CD8+ cytotoxic T-cell dysfunction in obesity and its implications in anti-PD-1 blockade therapy

In chronic conditions, notably cancers, CD8+ cytotoxic T cells gradually lose their effector functions due to constant exposure to antigens and consequent upregulation of inhibitory receptors like PD-1. In this regard, PD-1 blockade therapy was shown to bolster cytotoxic T-cell response and improve disease prognosis in some cases. PD-1 mediated T cell dysfunction is also involved in obesity-induced tumorigenesis. In this study, we used a molecular cytometry approach to better understand the disturbances caused by obesity in immune cells. A detailed single-cell analysis of various cell compartments revealed a unique population of CD8+ cytotoxic T cells in the epididymal fat of mice consuming a high fat diet for 16 weeks. These cells showed high expression of proteins and/or mRNA transcripts for various inhibitory receptors, including PD-1. Based on these results, we created a 28-color panel for high-throughput cell analysis at multiple time points over the 16-week period, using a BD FACSymphony™. The frequency of CD8+PD-1+ T cells in the fat correlated with the numbers of inflammatory cells, suggesting that the dysfunctional phenotype resulted from a growth in inflammation over time. The functional state of the CD8+PD-1+ cells was also examined by challenging these cells with or without PD-1 blockade. Taken together the data delineated a refined application for a broad analysis of immune cells in the fat and provided insights into the effects of obesity-induced T-cell dysfunction in mice. For Research Use Only. Not for use in diagnostic or therapeutic procedures. Class 1 laser product. BD, the BD Logo, FACSymphony is trademark of Becton, Dickinson and Company. © 2019 BD and its subsidiaries. All rights reserved.