F2R and chronic obstructive pulmonary disease: Immunofluorescent PAR-1 immunoreactivity was demonstrated in the distal airways: (1) inactive receptor (H111 Ab) (green colors), localized in the cell membrane, and total receptor (ATAP2 Ab) (red colors) predominantly in the cytoplasm of epithelial cells of HC; (2) low levels of the anti-inactive receptor (H111 Ab) (green colors) in the cell membrane, with a prevalence of the total receptor (ATAP2 ab) (red colors), localized in the cytoplasm of epithelial cells from COPD patients.