Changes and significances of CD4+ CD25highFOXP3+ regulatory T cells and its subsets in children with acute Kawasaki disease

Objective To investigate the changes and significances of CD4+CD25highFOXP3+ regulatory T cells (Treg) and its subsets in children with acute Kawasaki disease (KD). Methods Thirty-six children with KD and thirty-two age-matched healthy donors were studied. Flow cytometry was performed to evaluate the proportions of Treg and its subsets [inducible T-cell co-stimulator(ICOS)+ Treg and ICOS- Treg], and the expression levels of associated molecules such as interleukin (IL)-10, transform growth factor (TGF)-β, IL-35, TGF-βRⅡ, ICOS and CD28 were tested. Transcription levels of Smad family member (Smad) 3/4, TGF beta inducible early response gene 1 (TIEG1) and itchy E3 ubiquitin protein ligase (Itch) in CD4+ T cells were determined by quantitative real-time polymerase chain reaction (PCR). Plasma concentrations of TGF-β were measured by enzyme-linked immunosorbent assay. Independent-samples t-test was used as the statistical method in this study. Results ① The proportions of Treg and its subsets (ICOS+ Treg and ICOS- Treg) in children with acute KD [(3.2±1.8)%, (2.3±1.0)%, (0.9±0.3)%] were lower than those in healthy controls [(7.3±2.9)%, (4.7±1.4)%, (2.6±0.9)%; t=6.9, 11.7, 9.8; P<0.05], which resulted in a higher ratio of ICOS+ Treg/ICOS- Treg [(2.6±0.7) vs (1.8±0.5), t=9.4, P<0.05], and restored remarkably after therapy [(5.9±2.3)%, (3.9±1.6)%, (2.0±0.8)%, (1.9±0.5)%; t=5.5, 5.0, 8.2, 4.9; P<0.05]. ② Expression levels of FOXP3, IL-10, TGF-β, IL-35p35 and IL-35EBI3 in ICOS+ Treg of patients with acute KD were found to be lower than those in healthy controls (t=5.5, 4.8, 8.0, 6.6, 9.6; P<0.05). Meanwhile, FOXP3 and membrane bound TGF-β on ICOS- Treg in children with acute KD were lower than those of healthy subjects (t=7.5, 10.0; P<0.05), although expression levels of all the molecules mentioned before were elevated after therapy (t=3.7, 3.7, 8.5, 6.1, 7.7, 5.3, 7.0; P<0.05). ③ Plasma TGF-β concentration and expression levels of TGF-βRⅡ and its downstream molecules (Smad 3/4, TIEG1 and Itch) in CD4+ T cells of patients with acute KD were lower than those of healthy controls, while the expression levels of ICOS and CD28 on Treg of patients with acute KD were detected to be lower than those of healthy controls, respectively. All molecules mentioned above restored after therapy. Conclusion Insufficiency of TGF-β, ICOS and CD28 signaling maybe important for the impairment of Treg and imbalance of its subsets in children with acute KD. Key words: Mucocutaneous lymph node syndrome; T-lymphocytes, regulatory; Antigens, CD28; FOXP3; Inducible T-cell co-stimulator