Functional analysis of antigen-specific T lymphocytes by serial measurement of gene expression in peripheral blood mononuclear cells and tumor specimens

The cloning of cancer Ags recognized by T cells has provided potentially ne w tools to enhance immunity against metastatic cancer. The biological monit oring of effective immunization has, however, remained a dilemma. We descri be here a sensitive molecular quantitation methodology that allows analysis of in vivo immune response to vaccination. Metastatic melanoma patients we re immunized with a synthetically modified peptide epitope (209-2M) from th e melanoma self-Ag gp100, Using serial gene expression analysis, we report functional evidence of vaccine-induced CTL reactivity in fresh cells obtain ed directly from the peripheral blood of postimmunized patients. Further, w e demonstrate in vivo localization of vaccine-induced immune response withi n the tumor microenvironment, The results of these molecular assays provide direct evidence that peptide immunization in humans can result in tumor-sp ecific CTL that localize to metastatic sites.