OLIGOCLONALITY OF TUMOR-INFILTRATING LYMPHOCYTES FROM HUMAN MELANOMAS

A PCR-based method that determines VDJ junction size patterns in 24 hu man TCR VP subfamilies was used to analyze T cells infiltrating sequen tial malignant melanoma biopsies for the presence of clonal expansions . Infiltrating T cell populations were found to present clonal expansi ons over a more or less complex polyclonal background. Two clones from a single patient were sequenced and detected in three different tumor sites (skin biopsies), whereas only one of them was also present in p eripheral blood. Biopsies from this patient did not show major reperto ire changes during in vivo IL-2 treatment. In contrast, in biopsies fr om a second patient, the expression of all the detected V beta subfami lies was increased and a larger number of clones expanded, probably as a result of therapy. A similar evolution was found among infiltrating T cells cultured in vitro from a third patient for several weeks in t he presence of IL-2, where the largely polyclonal repertoire of fresh T cells (from invaded lymph nodes) was dramatically reduced to mainly clonal expansions in all V beta subfamilies detected. The high resolut ion method used here enables a rapid, comprehensive, qualitative, and semiquantitative description of the T cell repertoire of heterogeneous cell populations. Its use in conjunction with a functional analysis o f clones detected within these populations should provide a better und erstanding of the evolution of the T cell repertoire among tumor-infil trating lymphocytes during the progression of the disease and as a res ponse to immunotherapy.