INTRODUCTION: Pediatric tonsillitis is frequently caused by Staphylococcus aureus, which is the most common pathogen that causes serious pyogenic infections in humans and endangers human health. S.?aureus produces numerous potent virulence factors that play a critical role in the pathogenesis of the infection caused by this bacterium, and one of the most important toxins produced by S.?aureus is toxic shock syndrome toxin-1 (TSST-1). The aim of this study is to investigate the first time the levels of IFN-γ and interleukin IL-6 in TSST-1-stimulated PBMCs from pediatric tonsillitis patients and the correlation of these cytokine levels with TSST-1-specific IgG in serum. METHODS: TSST-1 gene of S.?aureus was cloned and expressed in a prokaryotic expression system, and purified recombinant TSST-1 protein was used for measuring TSST-1-specific antibodies in the serum of patients with pediatric tonsillitis caused by S.?aureus. Moreover, the levels of interferon (IFN)-γ and interleukin (IL)-6 in TSST-1-stimulated peripheral blood mononuclear cells (PBMCs) from pediatric tonsillitis patients were investigated. RESULTS: In patients with pediatric tonsillitis caused by S.?aureus, significantly higher levels of serum TSST-1-specific IgG (P?