It has been demonstrated in detail that administration of a dominant T-cell determinant to animals induces activation or immunological tolerance of T cells. However, it has not been determined whether multiple T-cell determinants, when integrated into a single peptide, retain their potential to induce T-cell activation and tolerance. We prepared a synthetic peptide comprising three T-cell determinants of Cry j 1 and Cry j 2, the major Japanese cedar pollen antigens, and investigated the immunogenicity and tolerogenicity of each T-cell determinant in the linked peptide by means of lymph node cell proliferation assays using mice. Lymph node cells from mice immunized with each of the three T-cell determinants proliferated against the linked peptide in a dose-dependent manner, similar to that of the immunized peptide. Lymph node cells from mice immunized with the linked peptide proliferated against all of the three T-cell determinants. In addition, the degree of proliferation against the three T-cell determinants occurred according to their original immunogenicity, as observed in the native protein antigens. Oral administration of the linked peptide to mice before they were immunized with Cry j 1 and Cry j 2 inhibited lymph node cell proliferation against the three T-cell determinants, depending on the dose of the linked peptide administered. In conclusion, it was demonstrated that three T-cell determinants retain their original immunogenicity and tolerogenicity in a linked peptide comprising them.