In vitro studies showed that blocking CD137 with an anti-CD137 antibody following PHA stimulation of PBMC from COPD patients resulted in a decrease in the percentage of CD8+CD28null NKT-like cells producing IFNγ, TNFα, and granzyme b production (26) compared with CD8+CD28+ NKT-like cells (Figure 2J), whereas stimulatory CD137 antibody increased production of these molecules. Here, TNFRSF9 is linked to chronic obstructive pulmonary disease.