[Immunoregulation and autoimmunity]

Peripheral tolerance to extrinsic antigens or autoantigens involves regulatory T cells, numerous but probably distinct types of which seem to exist. The investigation of their phenotype, of the cytokines on which they depend and the circumstances for their appearance allow classifying them into two categories: 1. Cells for which the appearance is observed independently of the deliberate administration of an antigen (CD25+ T cells, NKT cells, gamma/delta cells). 2. Cells which seem to intervene exclusively in response to the antigens introduced into the organism (Th2 cells, Tr1 cells). These various cells, whether related to innate or adaptive immunity, can be used to advantage as new therapeutic targets.