A CTL assay indicates the presence and cytotoxic activity of T cells to a specific antigen and allows to examine the influence of a test item on this immune function. The CTL response against T-dependent antigens requires the cooperation of at least three different major categories of immune cells. These include professional antigen presenting cells (e.g., dendritic cells), CD4(+) T helper lymphocytes, and CD8(+) T effector lymphocytes. It is also among the few functional responses dependent on and, hence, capable of evaluating effective antigen presentation via both class I and class II molecules of the major histocompatibility complex (MHC).
This assay allows the detection of cytolytic activity specific for a peptide epitope in-vivo in mice. One group of target cells is labeled with a higher concentration of CFSE dye and pulsed with the antigenic peptide epitope, while the other group of target cells is labeled with a lower concentration of CFSE and pulsed with an irrelevant peptide. They are mixed in a 1:1 ratio and injected i.v. into immunized and naïve mice. A deviation from the 1:1 ratio when the mice are sampled indicates specific lysis of the cells with the relevant epitope on the surface. Normal spleen cells are used as target cells.
Evaluating the influence of the test item on the presence and cytotoxic activity of T cells to a specific antigen.