Peptide/HLA-GFP Complexes

Abstract

Antigen-specific T cell responses are essential in host immune defense in health and disease. For many years, it was believed that the immune system was effective only in combating infectious diseases caused by invading agents such as bacteria and viruses. More recently, however, the immune system has been shown to play a central role in protection and recovery against cancer. This latter role is not well understood, but there are numerous reports that the immune system slows down the growth and spread of tumors in cancer patients. Many clinical trials for cancer immunotherapy are in progress and use anti-tumor vaccinations that have been designed to elicit antigen-specific T cell responses. Therefore, in defining anti-tumor immune responses that may be used for immunotherapy trials, the detection and quantitative analysis of antigen-specific T cell populations has been an important step toward understanding the cellular immune response in patients. In this chapter, we introduce a newly established system for the analysis of antigen-specific T cells, which is based on the technology using artificial antigen presenting cell expressing human leukocyte antigen (HLA)-A*201 coupled to the enhanced green fluorescent protein (GFP) (HmyA2GFP cells). Antigen-specific CD8+ T cells have been demonstrated to acquire peptide-major histocompatibility complex (MHC) clusters through T cell receptor-mediated endocytosis upon specific antigen stimulation. We generated an antigen-presenting cell expressing HLA-A*201 coupled to the GFP which when pulsed with antigenic peptide will deliver the GFP to an antigen-specific T cell. We demonstrated the quantitative identification of human T-cell lymphotropic virus type I (HTLV-I) Tax11-19 peptide-specific T cell populations in peripheral blood mononuclear cells from patients with HTLV-I associated neurologic disease and defined a novel CD8+ T cell epitope in the HTLV-I Envelope region.