VISUALIZATION OF ANTIGEN-SPECIFIC T-CELL ACTIVATION AND CYTOKINE EXPRESSION IN-VIVO

A transgenic TCR adoptive transfer system was used to visualize Ag-spe cific T cell activation and cytokine expression in vivo. After s.c. in jection of peptide in adjuvant the entire Ag-specific population up-re gulated IL-2 receptor alpha-chain expression, underwent blast transfor mation, and developed a memory-surface phenotype. A minority of the Ag -specific T cells produced predominantly IL-2 mRNA and localized at th e T cell/B cell junction in draining lymph nodes. In the secondary res ponse, a mixed cytokine pattern of both Th1 and Th2 cytokines was demo nstrated. When peptide was administered i.v. without adjuvant, 50% of the Ag-specific cells expressed IL-2, but the peak of expression occur red before IL-2 receptor alpha-chain up-regulation, and only a minorit y of the Ag-specific T cells underwent blast transformation.