• allergens, Japan;
  • house dust mite;
  • chironomid midge

To analyse the cross-reactivity of T-cell-mediated immunity between Dermatophagoides pteronyssinus (Dp) and Chironomus yoshimatsui (Cy), the most common allergens in Japan, we established antigen-specific human T-cell lines and clones. Some but not all of the Cy-induced T-cell lines showed a significant proliferative response not only to Cy, but also to Dp. No T-cell line responded to other unrelated antigens. When we stimulated the Dp-induced T-cell clones with Cy, 3 of the 40 clones (7.5%) showed a significant proliferation, and 2 of the 3 clones produced interleukin-4 and interferon-γ, indicating their helper function, Cross-reactivity was diminished significantly after the absorption of Dp antigen in an anti-Cy affinity column. The cross-reactive epitopes were thought to be expressed on the Dp molecule of 45–53 kD, The presence of helper T cells reactive to both allergens suggests a possibility that this cross-reactivity might be involved in part in the high incidence of allergy to the 2 major allergens.