β-(1→3)-Glucans can be found as structural polysaccharides in cereals, in algae or as exo-polysaccharides secreted on the surfaces of mushrooms or fungi. Research has now established that β-(1→3)-glucans can trigger different immune responses and act as efficient immunostimulating agents. They constitute prevalent sources of carbons for microorganisms after subsequent recognition by digesting enzymes. Nevertheless, mechanisms associated with both roles are not yet clearly understood. This review focuses on the variety of elucidated molecular interactions that involve these natural or synthetic polysaccharides and their receptors, i.e., Dectin-1, CR3, glycolipids, langerin and carbohydrate-binding modules.

A substantial proportion of long-term kidney graft recipients, including those with a stable renal function in the absence of immunosuppressive therapy, present a skewed T cell receptor (TCR) V␤ chain usage, essentially in the CD8 ؉ subset. This study analyzed in more detail phenotypical and functional alterations of CD8 ؉ lymphocytes in drug-free tolerant patients (DF-Tol) compared with recipients with chronic rejection (CR D rug-free tolerance, defined as long-term maintenance of graft integrity and function without immunosuppression, is a rare event in human kidney transplantation because interruption of immunosuppressive treatment usually leads to acute or chronic graft rejection. Nevertheless, this phenomenon is of unique interest to study the physiologic basis of graft tolerance in humans. On the one hand, long-term drug-free tolerant patients (DF-Tol) represent a unique model to study the extent to which mechanisms of tolerance defined experimentally, such as active suppression by regulatory lymphocytes, ignorance of alloantigens, chimerism, homeostatic regulation or clonal deletion, are relevant to this human situation (1-4). Most studies in rodents analyzed the induction rather than the maintenance phase of tolerance, and discrepancies with the human situation may exist, as exemplified by the role of alloreactive CD8 ϩ central memory cells in rejection and tolerance induction (5,6). On the other hand, the characterization of peculiar immunologic profiles in DF-Tol may be clinically important to identify biologic signatures that are associated with graft tolerance. Considering the major medical and economic burden of chronic immunosuppression and that operational tolerance may be more common than expected but could be masked in long-term immunosuppressed patients, the identification of specific biologic signatures of tolerance could open new perspectives for rational rather than empiric minimizing of immunosuppressive drugs in well-selected patients (6 -10).As a proof of concept of the relevance of the DF-Tol model to study human tolerance, we described recently a number of specific immunologic features in these patients. First, DF-Tol Received February 16, 2005. Accepted October 17, 2005 Published online ahead of print. Publication date available at www.jasn.org.S.B. and J.-P.S. contributed equally to this work.