Pyostomatitis vegetans: cellular immune profile and expression of IL-6, IL-8 and TNF-alpha

The aim of this study was to investigate the cellular immune profile and the expression of IL-6, IL-8 and TNF-alpha in tissue biopsies of pyostomatitis vegetans (PV). Working hypothesis was that knowledge of the cellular immune profile and role of mediators such as IL-6, IL-8 AND TNF-alpha may contribute to a better understanding of the pathogenesis of this rare entity. Archival tissues from three patients with clinically and histologically confirmed PV were studied. Analysis of the immune profile of the cellular infiltrate and expression of IL-6 and IL-8 were evaluated by immunohistochemistry. ISH was performed to evaluate the expression of TNF-alpha. Biopsy tissues from erythema multiforme, recurrent aphthous stomatitis, lichen planus and normal buccal mucosa were analyzed as controls. All patients were affected by multiple mucosal ulcerations and yellow pustules mainly located in the vestibular, gingival and palatal mucosa. Histopathologically, all specimens showed ulcerated epithelium with characteristic intraepithelial and/or subepithelial microabscesses containing abundant eosinophils plus a mixed infiltrate composed of lymphocytes and neutrophils. Cellular immune profile of the inflammatory infiltrate revealed a predominance of T-lymphocytes, mainly of cytotoxic (CD3+/CD8+) phenotype, over B-cells. CD20+ B-lymphocytes were also identified to a lesser degree among the lymphoid cells present in the lamina propria. Overexpression of IL-6 and TNF-alpha was found in both epithelial and inflammatory mononuclear cells. IL-8 expression was shown in the mononuclear cells scattered among the inflammatory infiltrate. Similar findings of overexpression of IL-6, IL-8 and TNF-alpha were, however, found in control tissues. In PV lesions, the inflammatory infiltrate shows a predominance of cytotoxic lymphocytes. Expression of IL-6, IL-8 and TNF-alpha, although not specific to PV, appears up-regulated thus these cytokines would represent a suitable therapeutic target. However, the complexity of the cytokine network and their numerous functions require further studies in order to confirm our findings.