Japanese cedar pollens (JCPs) spread over most areas of Japan from February to April and cause pollenosis. While IgE synthesis against JCPs starts after age 1, it remains to be clarified when JCP-specific T helper cells acquire the ability to produce IL-4, a cytokine that induces IgE synthesis.Objective
This study aimed to clarify when the sensitization of T cells to JCPs develops.Methods
Peripheral blood mononuclear cells from 153 children with atopic dermatitis (AD) aged 0–15 years were stimulated with a standardized JCP allergen. As parameters of T cell responsiveness, lymphocyte proliferation and the production of IL-4 and IFN-γ were measured.Results
T cell responses against JCPs were negative before March in infants with AD who had never been exposed to JCPs or who were exposed for less than a month (nine, seven and nine subjects for lymphocyte proliferation, cytokine production and IgE synthesis, respectively). Lymphocyte proliferation distinctly increased in 67.6% (23/34) of infants with AD examined between March and June. JCP-specific IL-4 production was observed in 56.0% (14/25) of infants with AD examined between March and June. Correspondingly, a slight increase in the level of serum JCP-specific IgE antibody was seen in 17.2% (five of 29) of infants with AD examined between April and June.Conclusion
These results demonstrate that the sensitization of T cells to JCPs is effectively completed within a few months after the first exposure to JCPs.