Background: Antigen-specific CD8+ cytotoxic T lymphocytes represent potent effector cells of the adaptive\r\nimmune response against viruses as well as tumours. Therefore assays capable at exploring the generation and\r\nfunction of cytotoxic T lymphocytes represent an important objective for both clinical and experimental settings.\r\nMethods: Here we show a simple and reproducible assay for the evaluation of antigen-specific CD8+ cytotoxic T\r\nlymphocytes based on a LysiSpot technique for the simultaneous determination of antigen-specific IFN-g\r\nproduction and assessment of tumor cytolysis. The assay was developed within an experimental model of\r\ncolorectal carcinoma, induced by the colorectal tumor cell line DHD-K12 that induces tumors in BDIX rats and, in\r\nturn, elicits a tumor- specific immune response.\r\nResults: Using DHD-K12 cells transfected to express Escherichia coli b-galactosidase as target cells, and by the fine\r\nsetting of spot colours detection, we have developed an in vitro assay that allows the recognition of cytotoxic T\r\nlymphocytes induced in BDIX rats as well as the assessment of anti-tumour cytotoxicity. The method highlighted\r\nthat in the present experimental model the tumour antigen-specific immune response was bound to killing target\r\ncells in the proportion of 55%, while 45% of activated cells were not cytotoxic but released IFN-g. Moreover in this\r\nmodel by an ELISPOT assay we demonstrated the specific recognition of a nonapeptide epitope called CSH-275\r\nconstitutionally express in DHD-K12 cells.\r\nConclusions: The assay proved to be highly sensitive and specific, detecting even low frequencies of cytotoxic/\r\nactivated cells and providing the evaluation of cytokine-expressing T cells as well as the extent of cytotoxicity\r\nagainst the target cells as independent functions. This assay may represent an important tool to be adopted in\r\nexperimental settings including the development of vaccines or immune therapeutic strategies.
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