Flow chart of the possible kinetics of interactions between melanoma and alphabeta T cells of tumor-bearing patients. Early T cell response may or not be activated (left, central and right upper panel). If activated (left and central panel), T cells can preferentially recognize strongly immunogenic unique antigens. T cell recognition may result in either complete or partial reduction of the most immunogenic and metastasis competent tumor cells. Patients whose immunogenic/metastasis competent cells are eliminated will then be cured by surgery (left panel), whereas partial elimination of such neoplastic cells will allow recurrences to occur in at least a fraction of the patients. Patients in whom no immune recognition in the primary lesion takes place (right panel) will recur with a high frequency. Vaccination of metastatic patients with antigens which have been selected against during tumor growth will be ineffective due to the lack or low expression of common differentiation antigens and the useless high frequency of CTLps directed to unique antigens, these unique antigens not being included in the vaccine. However, patients whose T cells failed to recognize unique and/or differentiation antigens during tumor growth could be prone to respond to vaccines containing differentiation antigens should the vaccine formulation result in priming of naive T cells (e.g. using DC) that can find their target (differentiation antigens) or the antigenically unselected tumor cells.