[Allogenic reaction, a model of autoimmunity]

Allogenic diseases induced in rodents by the inoculation of foreign lymphocytes represent useful models to investigate the mechanisms governing the activation of autoreactive B cells in systemic lupus erythematosus and related autoimmune disorders. The role of CD4+ helper T cells recognizing foreign class II MHC molecules has been particularly well established in murine chronic graft-versus-host disease and host-versus-graft disease. The T cells involved in these models essentially produce interleukin-4 and interleukin-10, which corresponds to the phenotype of Th2 cells. The association between autoimmunity and cellular immunodeficiency in experimental allogenic diseases could therefore be directly related to the hyperactivity of Th2 cells. Similar mechanisms might be operative in human systemic autoimmune diseases as well as in other clinical settings such as graft-versus-host disease after bone marrow transplantation or the acquired immunodeficiency syndrome.