Salivary gland involvement in graft-versus-host disease: the underlying mechanism and implicated treatment

Patients with graft-versus-host disease suffer from xerostomia, oral infections and mucosal pathologies. The continuous increase in the number of patients treated with bone marrow transplants worldwide, combined with improved survival statistics result in a concomitant increase in the number of GVHD patients. The pathogenesis of GVHD is based on donor graft T lymphocytes that recognize antigenic disparities between donor and recipient, and on the disregulation of a broad panel of cytokines. Consequently, various tissues and organs, including the mucosa of the oral and gastrointestinal tract, are damaged via cytotoxicity caused by infiltrating T cells. Since the salivary glands are a known major target of GVHD and their secretions significantly contribute to preserving mucosal integrity, this mucosal insult is further enhanced by the reduced quantity and altered quality of saliva. GVHD occurs in 40-70% of patients treated by bone marrow and peripheral blood stem cell transplantation. Limited studies suggest that a large percentage of GVHD patients are affected and that the induced salivary dysfunction occurs rapidly following transplantation, affecting both major and minor salivary glands and reflecting the severity of the disease. Moreover, profound sialochemical alterations may be diagnostic of GVHD. An additional reason for the vast amount of research is that GVHD, as an autoimmune-like disease, seems to be an appropriate model for studying a much more prevalent, well-known and studied autoimmune disease involving salivary glands, namely, Sjögren's syndrome. The present review describes the GVHD-related sialometric and sialochemical data available in the literature for both major and minor salivary glands in both human and rodent models, and discusses a possible mechanism.