Purpose/Principle

Global measurement of mitogen-induced T cell proliferation is useful for the assessment of immune deficiency and quality of immune reconstitution following hematopoietic stem cell transplantation (HSCT). Assessment of antigen-specific proliferation is routinely used when there is suspicion for impaired ability to generate an antigen-specific T cell response. The radioactive tritiated thymidine assay, which has been used for this purpose over the past decades, cannot specifically distinguish proliferating T cells in a peripheral blood mononuclear cell (PBMC) culture. Here, we assess the utility of flow cytometry to measure antigen-specific T cell proliferation following stimulation with tetanus toxoid (TT) utilizing the Click-iT technology, which incorporates a fluorescent dye into DNA of actively dividing cells. By also labeling cells with specific surface markers, this method provides advantage over the tritiated thymidine lymphocyte proliferation assay by discriminating specific proliferating cell populations while also measuring antigen-specific responses in memory T cells. As nearly most individuals are vaccinated with TT, this T cell dependent recall antigen can be used to monitor the immune response of individuals.