A user-friendly, highly sensitive assay to detect the IFN-γ secretion by T cells

Objectives: Development of a user-friendly test alternative to ELISA-based assays to detect IFN-γ by in vitro cultured peripheral blood mononuclear cells (PBMC) stimulated with pathogen-derived antigens. Design and methods: The molecular components of an operational IFN-γ ELISA-based test were applied in a lateral flow (LF) immunosandwich assay using up-converting phosphor (UCP) reporter particles. The analytical sensitivity of the UCP-LF IFN-γ assay (ULIGA) was determined and the assay was qualitatively validated with a selection of 60 supernatants derived from PBMC cultures stimulated with M. leprae derived antigens, mitogen or medium alone. Results: ULIGA indicated an analytical sensitivity better than 2 pg/mL, and demonstrated four orders of magnitude dynamic range. The assay correlated well with the IFN-γ ELISA. Conclusions: ULIGA allows detection well below the cutoff value (100 pg/mL) used to define positive responses in the IFN-γ ELISA. The test procedure is less demanding in respect to equipment and labor, and is suited for testing single samples.