Immune response profiling and monitoring are widely acknowledged as key elements in the development of new biotherapies-particularly in auto-immune disorders,infectious diseases,cancer,transplantation,allergies and vaccine development.CTL provides abundant experience in working with various assays for monitoring T and B cell immunity.Defining frequencies of antigen-specific T cells is one of the primary goals of ex vivo T cell diagnostic testing.Na(i)ve T cells can clonally expand and differentiate after antigen encounter (for example,after infection or vaccination) to give rise to a CMI response.In addition,while measuring the cytokine signatures or cytolytic potential of antigen-specific memory/effector cells,it is important to know how many such T cells have been induced.The frequency of the antigen-specific T cells from freshly isolated cellular material,such as blood,spleen or lymph nodes,provides valuable information about the magnitude of T cell immunity.