This experimental setting allowed us to investigate the capacity of adoptively transferred TRP-1 CD4+ T cells to indirectly recognize and kill IFN-unresponsive, MHC-deficient tumour cells independent from their ability to directly target and lyse MHC-II-expressing tumour cells and to provide help for the cytolytic activity of CD8+ T and NK cells. The gene discussed is HLA-C; the disease is neoplasm.