OBJECTIVEMany clinical evidences and epidemiologic data in the past suggested that Kawasaki disease (KD) is correlated with an acute immune dysfunction caused by infection. In our preliminary study, Toll-like receptor 4 signal pathway, which could activate nuclear transcription factor-kappaB and induce excessive product of proinflammatory cytokines, chemokines and co-stimulatory molecules, was observed to be significantly activated during acute phase of Kawasaki disease. But the causative factors and regulatory mechanism are still unknown. In this study, the authors further investigated the changes and significances of regulatory factors for signal pathway of Toll-like receptors (TLRs) in immunological pathogenesis of Kawasaki disease.

METHODSForty-eight children with KD, sixteen children with infectious disease (ID) and sixteen age-matched healthy children were studied. Reverse-transcription PCR (RT-PCR) and real-time PCR were used to evaluate the expression levels of regulatory and effective factors in toll-like receptor 4 (TLR4) signal pathways and proinflammatory factors in peripheral blood monocyte/macrophage (MC). The expression of TLR4 protein in MC was analyzed by flow cytometry.

RESULTS(1) Expression levels of TLR4, MD-2, MyD88, IRAK-4, TRAF6, TAK1, TAB1 and TAB2 mRNA in KD group were elevated significantly during acute phase (P < 0.05). (2) Transcription levels of regulatory factors PRAT4B and STAP2 in patients with KD or ID were found to be higher than those in the healthy volunteers (P < 0.05), but no significant differences in these parameters were detected between KD patients and ID patients (P > 0.05). Transcription levels of regulatory factors such as FLN29, RP105 and MD-1 were up-regulated to some extents and expression level of DAP12 mRNA in KD patients were found to be lower than that in normal controls (P < 0.05), while all of the four regulatory factors were found to be lower than those in ID patients (P < 0.05). Expressions of proinflammatory cytokines such as L-1beta, IL-6 and TNF-alpha in KD patients were significantly higher than those in ID patients (P < 0.05). (3) Stimulation with lipopolysaccharide (LPS) elevated remarkably the expressions of regulatory factors PRAT4B and STAP2 in KD patients or healthy volunteers (P < 0.05). All of the four negative-regulatory factors were found to be significantly up-regulated after stimulation with LPS in controls (P < 0.05). No responses to LPS were observed in expression of FLN29, RP105 and MD-1 mRNA in KD patients (P > 0.05), except for increased transcription of DAP12. (4) The levels of PRAT4B and STAP2 mRNA in KD patients with coronary artery lesion (KD-CAL(+)) were detected to be higher than those in KD patients without coronary artery lesion (KD-CAL(-)) during acute phase (P < 0.05), while those of FLN29, RP105 and MD-1 in KD-CAL(+) group were lower than that in the latter (P < 0.05). No significant difference in DAP12 mRNA expression level was detected between the two groups (P > 0.05). Expressions of proinflammatory cytokines and TLR4 protein on surface of CD14-positive cells in KD-CAL(+) group were found to be higher than those in KD-CAL(-) group [(11.9 +/- 2.4)% vs. (6.5 +/- 1.7)%, P < 0.05].

CONCLUSIONDisturbance of negative-regulatory factors may be one of the factors causing aberrant immunological function in KD.