CD4 and hypersensitivity pneumonitis: In contrast, a CD4/CD8 T lymphocyte ratio exceeding 1.5, which lacked predictive value in other lung diseases (5.9 vs. 5.7 years, p = 0.879), was associated with significantly shorter third-quartile overall survival (Q3-OS) in HP patients (8.9 years vs. not reached, p = 0.011) (Figure 5).