Bacterial biofilm is associated with higher levels of regulatory T cells in unaffected hidradenitis suppurativa skin

BACKGROUND: The role of bacterial biofilm in hidradenitis suppurativa (HS) is highly debated. Less biofilm is found in clinically unaffected axillary perilesional skin of HS patients compared with healthy controls. OBJECTIVE: To study the correlation between biofilm and the phenotypical characterization of the preclinical inflammatory infiltrate. MATERIALS AND METHODS: An exploratory comparative study of punch biopsies from unaffected axillary HS skin compared to similarly biopsies from healthy controls underwent standard staining procedures for CD4, CD8, CD25, FoxP3 and IL17. Standard-sized inflammatory histological hotspots were identified manually. Slides were scanned into Leica Biosystems' Digital Image Hub. Number of stained cells per slide and hotspot was found using an algorithm. RESULTS: 12.5% of HS had biofilm compared to 85% of controls. For full slides, HS patients had more CD4+ cells than controls; HS patients with biofilm had higher CD4+ cell number than controls with or without biofilm and HS patients without biofilm. For hotspots, HS patients with biofilm had higher number of CD4+FoxP3+ cells than HS patients without biofilm and controls with biofilm. CONCLUSION: The association between biofilm and the number of regulatory T cells in HS patients supports the concept of dysbiosis as a factor in the preclinical HS lesions.