Immunohistochemical characterisation of the interstitial inflammatory environment

\(\bf Background:\) Hidradenitis suppurativa (HS) is a chronic inflammatory disease with a complex immune response. Given the considerable heterogeneity of the clinical phenotype of HS, this study aimed to analyse the immunohistochemical pattern of interstitial inflammation. \(\bf Methods:\) Immunohistochemical analysis was performed on skin samples from 49 patients with HS. The immunohistochemical markers CD3, CD4 and CD8 for T-cells, CD20 for B-cells, CD138 for plasma cells and CD30, CD56, Bcl-2 and Bcl-6 were stained on lesional skin. \(\bf Results:\) The analysis of immune cell dominance in patients with HS revealed that 33.3% of the cohort exhibited B-cell dominance, defined as a ratio of the sum of CD20+ and CD138+ cells to CD3+ cells greater than 1, while the majority (66.7%) demonstrated T-cell dominance, defined as a ratio of CD3+ cells to the sum of CD20+ and CD138+ cells greater than 1. B-cell-dominant HS is associated with a significantly elevated probability of mammary involvement (13.3% vs. 0%; \(\it p\) = 0.041). T-cell-dominant HS patients tended to demonstrate a higher mean tobacco consumption, but not significantly (20 vs. 5 tobacco pack-years; \(\it p\) = 0.06). CD4-dominant HS patients exhibited a significantly greater involvement of the mons pubis (62.5% vs. 28.6%, \(\it p\) = 0.023) compared to CD8-dominant patients, who demonstrated a significantly higher number of abscesses (\(\it p\) = 0.027). \(\bf Conclusions:\) For the first time, we describe the clinical and immunohistochemical characteristics of T-cell- and B-cell-dominant HS. Although HS seems to be more dominated by T-cells, a B-cell dominance was found in 33% of cases.