Altered expression of the CD26/ADA axis in immune-mediated inflammation of infectious mononucleosis

Infectious mononucleosis (IM), a common disease in children, was often accompanied by excessive inflammatory response and organ damage. This study aimed to explore the CD26/ADA axis in the pathogenesis of acute Epstein-Barr virus (EBV)-associated IM. Thirty children with acute IM and thirty age-matched controls from Children’s Hospital of Soochow University were enrolled in this study. The CD26 and adenosine deaminase (ADA) mRNA were detected by real-time PCR in the peripheral blood. Meanwhile, the levels of plasma interferon gamma (IFN-γ), interleukin (IL)-4 and IL-10 were measured by ELISA, and the frequency of CD26-positive cells in CD4+ T cells and CD8+ T cells was analyzed by flow cytometry. Children with acute IM had significantly higher expression levels of CD26 mRNA and ADA mRNA than control group in peripheral blood (P < 0.05). Plasma IL-4, IL-10 and INF-γ level were markedly elevated compared to the control group (P < 0.05). Furthermore, the plasma CD26 protein level was positively correlated with ADA (r = 0.610, P<0.01) and INF-γ (r = 0.417, P = 0.022), and negatively correlated with the percentage of CD3+ CD4+ T cell (r = -0.446, P = 0.014) and CD4+ /CD8+ ratio (r = -0.414, P = 0.023) in acute IM group. In addition, the frequency of CD26-positive cells was elevated on CD8+ T cells but markedly decreased on CD4+ CD39+ regulatory T cells (P < 0.05). The peripheral blood CD26 and ADA mRNA levels were elevated in acute IM. Moreover, CD26 exhibited cell-specific alterations, being increased on CD8+ T cells but reduced on CD4+ CD39+ Tregs.