Background Kawasaki disease (KD) is an acute systemic vasculitis that primarily affects infants and young children below 5 years old. The cause of KD is still unknown, but the acute phase of KD is often accompanied by the alteration of circulating immune cells. The polyclonal activation of B cells during the course of disease is well documented.
Objectives In this study, the evidence of B cell activation and the possible involvement of superantigen in KD were sought.
Results In 13 out of 15 KD patients, an increase in B cells expressing the VH3 family was seen during the acute phase of disease. Analysis of B cell clonal expansion showed the VH6 family clone of 9 amino acids to be the most common, observed in 5 out of 15 KD patients. Analysis of CDR3 size profile showed that various prominent bands appeared during the acute phase of disease, and some disappearing during the subacute phase, while other newly developed bands appeared during the subacute phase of disease. The DNA sequences of CDR3s showed no dominant clone.
Conclusion These data suggest that KD may be caused by conventional antigen (s).