Polyclonal expansion of TCRBV2- and TCRBV6-bearing T cells in patients with Kawasaki disease

We examined T-cell receptor (TCR) usage, cytokine production and antibody r esponses to superantigens in patients with Kawasaki disease (KD) to facilit ate a better understanding of the immunopathogenesis of KD. The mean percen tage of VB2- or VB6.5-bearing T cells in peripheral blood mononuclear cells (PBMC) of patients with acute-phase KD was significantly higher than that of patients in the convalescent phase of KD or in healthy donors. Expansion of VB2- or VB6.5-bearing T cells was polyclonal because DNA sequences in t he complementarity determining region 3 of VB2- and VB6.5-positive cDNA clo nes were all different from each other. The plasma levels of interleukin (I L)-1 beta, IL-2, IL-6, IL-8, IL-10, interferon-gamma (IFN-gamma), tumour ne crosis factor-a (TNF-a) and granulocyte colony-stimulating factor (G-CSF) w ere elevated in the acute phase of KD. We previously reported that streptoc occal pyrogenic exotoxin C (SPEC) was a potent stimulator of VB2- and VB6.5 -positive T cells and, furthermore, serum levels of anti-SPEC antibodies we re significantly higher in patients with acute and convalescent KD than in age-matched controls. The results of the present study, together with those of our previous report, suggest that SPEC induces activation and polyclona l expansion of VB2- and VB6.5-positive T cells, and that SPEC-induced activ ation of T cells may lead to the pathogenesis of KD.