Of Omenn and mice

Omenn syndrome (OS) is a peculiar immunodeficiency in which profound T and B cell defects are associated with severe autoimmune-like manifestations . Although the molecular and biochemical basis of OS have been elucidated, the mechanisms leading to T cell infiltration of peripheral tissues such as skin and gut still remain unsolved. Two murine models with hypomorphic mutations in rag genes reproducing OS features and a murine model of lymphopenia-derived autoimmunity with similar immunopathology were recently described. The aim of this review is to integrate clues on the roles of impaired thymic development and lymphopenia in the pathogenesis of autoimmunity.