ELISPOT analysis of T-cell activation. T cells were stimulated with DCs loaded with tumour antigen (mRNA or apoptotic cells) or control DCs as indicated. (a) Mean number of IFN-γ positive spots obtained with the indicated numbers of un-fractionated T cells, and CD4+ and CD8+ T-cell subsets from individual donors. (b) Frequency of reactive T cells. The data represent mean values of all donors calculated by the formula: [(spots loaded DC - spots control DC)/105 T cells].