Abstract: 【Abstract】 Objective To determine the expression of T follicular helper （Tfh）cell?related molecules inducible costimulator （ICOS） and programmed cell death 1 receptor （PD?1） in skin lesions of patients with bullous pemphigoid （BP）, and to explore the role of Tfh cells in the pathogenesis of BP. Methods??? Twenty?one paraffin?embedded tissue specimens were collected from 21 patients with confirmed BP in Dalian Dermatosis Hospital from 2014 to 2017, including 7 females and 14 males with an average age of 72.57 years. Ten normal skin tissues served as control group. Immunohistochemical SP method was used to determine the expression of ICOS and PD?1 in BP skin lesions and normal skin tissues. Results In BP lesions, ICOS and PD?1 were mainly expressed in the basal layer, spinous layer, granular layer and stratum corneum, especially in the spinous layer. Additionally, they were both expressed in the cytoplasm and nuclei, occasionally expressed on the cell membrane, and also expressed in inflammatory cells in the dermis. However, ICOS and PD?1 were rarely expressed in the normal skin tissues. The expression rates of ICOS and PD?1 were significantly higher in the BP group （85.71% ［18/21］, 47.62% ［10/21］, respectively） than in the normal control group （both were 0; P < 0.001, < 0.05, respectively）. Conclusion Tfh cell?related molecules ICOS and PD?1 may play important roles in the pathogenesis of BP.

Key words: Pemphigoid, bullous, Programmed cell death 1 receptor, T-lymphocytes, helper-inducer, Inducible costimulator, T follicular helper cells