CD4 and chronic obstructive pulmonary disease: In COPD, the role of iNKT cells is as confounding with CD4+ iNKT numbers in the BAL and sputum unchanged, although a conflicting study reported that the frequency of iNKT cells in the peripheral blood was significantly reduced in subjects with COPD compared to healthy individuals and further reduced in those COPD patients with exacerbations (117, 119).