Summary   Background The skin lesions found in patients with dermatitis herpetiformis (DH) are characterized by the presence of neutrophils at the dermal papillary tips in areas where the diagnostic cutaneous IgA deposits are found. Although the presence of the skin lesions of DH is known to be associated with gluten‐sensitive enteropathy, the mechanisms that control the development of skin lesions are not known.

Objectives To determine if circulating neutrophils from patients with DH have evidence of priming as shown by increased expression of CD11b, decreased expression of L‐selectin and increased function of neutrophil Fc IgA receptor.

Methods Neutrophils from 12 normal subjects and 10 DH patients with active, ongoing disease and 14 DH patients with quiescent disease activity were examined by fluorescence‐activated cell sorter for expression of cell surface CD11b, L‐selectin expression, Fc IgA expression (CD89) and for the function of the Fc IgA receptor by determining the binding capacity of neutrophils for monoclonal human IgA.

Results Neutrophils from patients with active, ongoing DH had increased expression of CD11b when compared with patients with inactive DH or normal subjects [mean net geometric mean channel fluorescence (GMCF): active DH, 403·3; inactive DH, 237·8; normal subjects, 290·5; P < 0·05]. L‐selectin expression in both groups of DH patients was significantly lower than that seen in normal subjects (mean net GMCF: active DH, 363·2; inactive DH, 375·2; normal subjects, 432·7; P < 0·05). No difference in CD89 expression was seen in any of the groups; however, the function of Fc IgA receptor was increased in patients with active DH when compared with patients with inactive DH and normal subjects.

Conclusions Neutrophils from patients with active, ongoing DH show an increased expression of CD11b, decreased expression of L‐selectin and increased ability to bind IgA, consistent with a pattern of priming of the neutrophils. This priming may occur in the gut as a result of the ongoing mucosal immune response that is present in patients with DH on a gluten‐containing diet and may predispose neutrophils to localize in the skin of patients with DH.