CD8A and hypersensitivity pneumonitis: Also, the elevated CD4/CD8 ratio seen in the BALF in hot tub lung is not typical for HP, although there are reports of variable or increased ratios described with farmer’s lung (Ando et al. 1991; Cormier et al. 1987), lifeguard lung (Rose et al. 1998), and HP of mixed etiology (Costabel et al. 1984) and that related to intravesical instillation of Bacillus Calmette-Guerin (Israel-Biet et al. 1987).