CD4 and chronic obstructive pulmonary disease: TRM CD4+ (CD69+CD25-HLA-DR-) and TRM CD8+ (CD69+CD25-HLA-DR-) cells constituted the majority of CD69+ CD4+ and CD8+ T cells and were comparably represented across COPD, IPF, and healthy donor lungs (35.4–51.6% [16.5–59.2] and 26.7–28.7% [17.1–70.6], respectively; Table 2).