Exploring the immunological basis of periodic fever, aphthous stomatitis, pharyngitis, and adenitis (PFAPA) syndrome: immunohistochemical staining features of palatine tonsils.

• The cessation of attacks following tonsillectomy points to fundamental role of tonsil tissue on etiopathogenesis of disease, which is not clarified satisfactorily. • In current study, 92.3% of our patients did not experience any attacks following operation similarly with literature. • We observed the increased number of CD4+ and CD8+ T cell counts on PFAPA tonsils compared to control group and emphasized the active role of both CD4+ and CD8+ cells localized on PFAPA tonsils in immune dysregulation. • Some other cell types evaluated in this study such as CD19+ (B cells), CD1a (dendritic cells), and CD123 (IL-3 receptors, for pluripotent stem cells) and H. pylori did not differ in PFAPA patients compared to the control group.