| Description |
Organizers:
Prof. Kenneth Rock (UMASS Medical School, USA)
Dr. Philippe Pierre (CIML, CNRS, France)
Aim of the conference:
Antigens only become visible to T lymphocytes when they are displayed on the cell surface bound to various antigen-binding molecules. In this process protein antigens are cleaved and presented as oligopeptides bound to Major Histocompatibility antigens (MHC) class I or class II molecules and lipid antigens are bound to CD1 molecules. T lymphocytes circulate looking for these complexes and if they find ones that they can recognize are then stimulated. This process of antigen presentation is of fundamental important because it not only controls whether T cell responses will be generated but also the kind of response (e.g. cytotoxic, helper, or regulatory) as well as its magnitude, specificity and location. Moreover, it directs T lymphocytes to interact with specific cells, allowing them to recognize and eliminate ones that are infected or transformed, instruct B cells to make antibody or stimulate macrophages to kill pathogens. In addition, antigen presentation also plays an essential role in the differentiation of T lymphocytes and the elimination or control of autoreactive cells (tolerance). Because of this antigen presentation is central to host defense to many pathogens and for generating protective responses to vaccines. On the other hand, defects in this process underlie disease susceptibilities including infections, autoimmunity, and cancer. Therefore, antigen presentation plays a central role in a number of processes of fundamental importance.
To accomplish these important functions the immune system has evolved several different antigen presentation pathways that monitor different kinds of cells and distinct compartments in the body. These pathways include: (1) The “endogenous” MHC class I pathway in which antigens in the cytosol of all cells are cleaved into peptides a fraction of which are bound and displayed by MHC class I molecules. This allows CD8 effector T cells to monitor the proteaome and identify cells that are virally infected or cancerous; (2) The MHC class I cross presentation pathway in which dendritic cells in which proteins from the environment are acquired and displayed as peptides bound to MHC class I molecules. This plays a key role in the immune surveillance of tissues for viral infections and cancers and also in immune tolerance. (3) The MHC class II pathway in which antigens internalized into the endocytic compartments of B cells, macrophages and dendritic cells are cleaved into peptides that are bound and displayed by MHC class II molecules. This process allows CD4 T cells to monitor antigens is the extracellular environment and respond in ways that generate CD4 T cell, antibody and/or inflammatory responses; and (4) The CD1 pathway in which lipid antigens present in the vesicular compartment of various cells are presented on CD1 molecules. This process allows innate like T cells to recognize phagocytes infected with microbes.
The antigen presentation pathways are the subject of very active research and there are major advances underway that are increasing our understanding of these critical processes. Therefore, we are proposing to convene an international workshop to share information about these major advances and also to highlight the problems remaining to be solved. The workshop will assemble the leaders in the field in an intimate and collegial environment to discuss these issues.
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