Contribution of LCMV Transgenic Models to Understanding T Lymphocyte Development, Activation, Tolerance, and Autoimmunity

T cells play a central role in the elimination of both intracellular and extracellular pathogens. Expression of the αβ T cell receptor (TCR) heterodimer enables T cells to specifically recognize peptides presented by major histocompatibility complex (MHC) molecules and generate an immune response to those peptides. CD4+ helper T cells are restricted to MHC class II molecules, and produce cytokines to augment T and B cell responses. CD8+ T cells are restricted to MHC class I molecules, and are generally cytotoxic T lymphocytes (CTLs) whose effector function involves the lysis of infected cells. Broad issues in T cell biology include how mature T cells develop from bone marrow-derived precursors and how T cell activation is regulated. These questions and others have been addressed in many models, including murine TCR transgenic systems, in which the transgenic expression of TCR chains provides a clonal population of antigen-specific T cells that can be readily monitored.