Principi di immunobiologia del trapianto ed attivazione della risposta immune

To achieve an effective immune response it is important that T cells can recognize a wide variety of non-self antigens; this allows for restrained immune activation and subsequent antigen-specific killing. This task is accomplished through the generation of a repertoire of T cells in a single individual with specificity for an enormous number of potential foreign antigens presented as peptides on the surface of major histocompatibility complex (MHC) molecules. Variations in MHC structure among individuals increase the variety of peptides that can be presented to T cells; this mechanism protects the species as a whole by ensuring adequate T-cell responses to a given foreign organism. Although slightly different, these MHC polymorphisms expressed in the donor kidney are recognized after kidney transplantation between non genetically-identical humans, and induce alloresponses that in the absence of immunosuppression result in rejection of the allograft. In this chapter, we review basic immunological principles important to the field of kidney transplantation