In ELISPOT assays, the gp100209–217 epitope-specific T
cells recognize PCI-13/IL-2/MEL DNA (recipient cells
transduced with DNA derived from gp100+ Mel 526) but not
the nontransduced PCI-13/IL-2 (A). The negative
controls (no T cells or T cells alone) had a very low background
(A). In B, positive and additional
negative controls from the same experiment are shown. Note that
gp100-negative melanoma (SLM-2) is not recognized, whereas
gp100+ Mel 526, the target for these T cells, induced a
large number of spots. HLA-A2 or HLA-DR Abs were used to block the
MHC-restricted responses in ELISPOT assays, as described in
Materials and Methods. The results were obtained in the
same ELISPOT assay for IFN-γ production. A representative experiment
of four performed is shown. The results in this and all other ELISPOT
assays shown are means ± SD from quadruplicate wells.