Application of the IFN-gamma ELISPOT assay to quantify T cell responses against proteins

The ELISPOT assay has been established for the direct ex vivo quantification of peptide-reactive T lymphocytes from peripheral blood mononuclear cells (PBMC). In this report we studied the ELISPOT assay conditions for the detection of T cell responses against protein antigens including Tetanus toxoid (TT), purified-protein-derivative (PPD) and a synthetic 30 mer peptide derived from influenza matrix protein (IMP) containing the HLA-A*0201-restricted 9 mer peptide epitope GILGFVFTL as a model for a viral protein. We found several aspects to be crucial for a sensitive detection of T cell responses against proteins including a pellet preincubation step and the monocyte concentration. Using optimized assay conditions specific CD4+ T cell responses against TT and PPD as well as CD8+ T cell responses against IMP can be quantified directly ex vivo from peripheral blood mononuclear cells.