Quantification of a change in phenotype of some epithelial cells was achieved by using involucrin staining graded with the criteria described in Fig 2, E. A significantly higher incidence of involucrin staining was observed for biopsy specimens from patients with moderate and severe asthma compared with healthy control samples (grade 3 [2-3] vs grade 0 [0-1], P < .001; grade 3 [2-3] vs grade 0 [0-1], P < .001; Fig 2, E) and biopsy specimens from patients with severe asthma compared with those from patients with mild asthma (grade 3 [2-3] vs grade 1 [0-2], P = .026). Here, IVL is linked to asthma.