Recruitment of abundant NK cells to the PFAPA tonsils support the crucial role of innate immunity in pathogenesis of PFAPA syndrome

Results During the asymptomatic phase the number of monocytes did not differ between the PFAPA and control tonsils. We observed a considerable recruitment of NK cells in tonsils of PFAPA patients with respect to CG. Surprisingly, we have detected a significant expansion of both CD56CD16 and CD56CD16NK cell subsets when compared to CG. Strict characterization of activating and inhibitory NK receptors revealed a crucial role of CD56CD16. Specially, activating receptors, such as natural cytotoxicity receptors (NCRs) and NKG2D, are higher in NK of PFAPA patients. Furthermore, FACS analysis displayed a higher number of naïve and a significantly lower percentage of effector memory CD4 and CD8 T cells in PFAPA patients compared to CG. Additionally, PFAPA patients presented a significant decrease of functional follicular helper T cells (Tfh) and regulatory T cells.