Complement activation in hidradenitis suppurativa: a new pathway of pathogenesis?

T. Kanni, O. Zenker, M. Habel, N. Riedemann, E.J. Giamarellos‐Bourboulis

Despite the heavy purulence observed in hidradenitis suppurativa (HS), kinetics of complement anaphylatoxins acting to prime chemotaxis of neutrophils has never been studied. Complement activation was explored in HS. Circulating concentrations of complement factor C5a as well as of membrane attack complex C5b-9 were determined in the plasma of 54 treatment naïve patients and of 14 healthy controls as well as in the pus of seven patients. Results were correlated with Hurley stage and iHS4 score of severity. Peripheral blood mononuclear cells (PBMCs) were isolated form seven Hurley III stage patients and seven healthy volunteers and stimulated in the presence of 25% of plasma for the production of tumor necrosis factor-alpha (TNFα). Circulating C5a and C5b-9 were significantly greater in patient than in control plasma; however concentrations in pus were very low. Circulating C5a levels exceeding 28 ng/ml were associated with specificity greater than 90% with occurrence of HS. Circulating C5a and C5b-9 were greater among the more severe patients. PBMCs of patients produced great TNFα concentrations only when growth medium was enriched with patient plasma; this was reversed with the addition of the C5a blocker IFX-1. Systemic complement activation occurs in HS and may be used as a surrogate biomarker of HS. C5a stimulates over-production of TNFα and may be a future therapeutic target. This article is protected by copyright. All rights reserved.