Article ViewAbstractThe Review of Diabetic Studies,2006,3,1,6-10.DOI:10.1900/RDS.2006.3.6Published:May 2006Type:EditorialAuthors:Deepak Yadav, and Nora Sarvetnick Author(s) affiliations:Deepak Yadav and Nora Sarvetnick The Scripps Research Institute, Department of Immunology, 10446, North Torrey Pines Road, IMM-23, San Diego, California 92037, USA. Abstract:T cell activation is a complex process that requires a multitude of interactions between antigen-presenting cells (APC) and T cells. The primary signal is provided via the binding of the antigen (Ag) presented by the major histocompatibility complex (MHC) on an APC and the T cell receptor (TCR). This signal determines the specificity of the immune response but it is not sufficient to mount an effective antigen- specific immune response; co-signals are additionally required for that purpose. These co-signals are costimulatory pathways that can be either positive or negative and consequently determine the nature of the immune response. The B7-1/2/CD28 costimulatory axis is one of the most extensively studied positive signaling pathways, and it has been shown that this signal leads to a robust T cell activation, proliferation and survival. In this article we discuss the recently described PD-1/PD-L1/PD-L2 costimulatory axis, whose role in pancreatic autoimmunity is only just becoming more deeply understood. The blockade or deficiency of PD- 1 leads to an exacerbation of diabetes, signifying that the role of PD-1 is to provide negative signals to T cells. On the other hand, the PD-1 ligand, PD-L1, has been shown to provide both positive and negative signals. The prediction of the existence of a non-PD-1 receptor on T cells capable of transmitting positive signals further adds to the complex nature of this costimulatory pathway. Keywords:Autoimmunity, Costimulation, PD-1, PD-L1, PD-L2, Type 1 diabetesView:PDF (231.65 KB) PDFClick here to download the PDF file. Images The positive or negative costimulatory behavior of PD-L1 may be governed by the relative availability of PD-1 and non PD-1 receptors on T cells ‹ The Review of Diabetic Studies, Vol. 3, Issue 1, 2006 up Eating Behavior among Type 2 Diabetic Patients: A Poorly Recognized Aspect in a Poorly Controlled Disease ›