Modest Expansion of Vβ2+CD4+ T Cells and No Expansion of Vβ7+CD4+ T Cells in a Subgroup of Kawasaki Disease Patients with Erythematic BCG Inoculation Site Lesions

Background: The similarities between Kawasaki disease (KD) and superantigen (SA) diseases indicate that a microbial SA might cause KD. Viral diseases can trigger an endogenous SA.Methods: We evaluated expression of Vβ2 (responding to staphylococcal TSST-1) and Vβ7 (responding to the endogenous SA induced by type-1 interferon or Epstein-Barr virus infection) on T cells from 70 KD patients along with the following control subjects: 18 non-vasculitic patients (NVs), 7 patients with anaphylactoid purpura (AP), and two with neonatal TSS-like exanthematous disease (NTED), a typical SA disease. We examined the correlation of clinical features of KD with Vβ2+ or Vβ7+CD4+T cell populations.Results: The Vβ2+CD4+T cell rates were comparable between KD patients (9.9±2.9%) and NVs (9.0±1.8%), but were lower in AP patients (6.6±1.8%). However, the Vβ2+CD4+T cell rate was significantly higher in KD patients with erythematic BCG inoculation site lesions (10.8±3.2%) than in those without (8.8±2.1%) and NVs (9.0±1.8%), but much lower than in NTED patients (25.2%, 16.9%). Multivariate linear regression analysis with elevation of Vβ2 expression as a dependent variable revealed significant correlations with BCG. In contrast, Vβ7+CD4+T cell rates were not significantly different between KD patients and other study subjects.Conclusion: While we were unable to find evidence supporting the involvement of the endogenous SA in the pathogenesis of KD in this study, modest expansion of the Vβ2+CD4+T cell population in a subgroup of KD with erythematic BCG inoculation site lesions implies the involvement of a microbial agent(s) different from TSST-1 as well as immunopathological heterogeneity of KD. (249 words