Oligoclonal T-cell receptor usage of melanocyte differentiation antigen-reactive T cells in stage IV melanoma patients

Ex vivo ELISPOT analysis of peripheral blood lymphocytes obtained from stag e IV melanoma patients demonstrated reactivity against peptides derived fro m MART-1 and gp100. However, the number of reactive T cells was <1% that of total lymphocytes as detected by flow cytometry using tetrameric MHC/pepti de complexes. Despite this low frequency, we were able to directly isolate these populations ex vivo by means of magnetic beads coated with MHC/peptid e complexes and to subject these cells to T-cell receptor clonotype! mappin g. This analysis revealed that the MART-1/A*0201- and gp100/A*0201-reactive T-cell populations are composed of oligoclonal T cells that engage several T-cell receptor <beta> chain families. Longitudinal studies using this app roach may result in a better correlation between T-cell reactivity and the course of neoplastic disease.