Regulation of MHC class II expression, a unique regulatory system identified by the study of a primary immunodeficiency disease

Tissue Antigens. 2006 Mar;67(3):183-97. doi: 10.1111/j.1399-0039.2006.00557.x.


Major histocompatibility complex class II (MHC-II) molecules are of central importance for adaptive immunity. Defective MHC-II expression causes a severe immunodeficiency disease called bare lymphocyte syndrome (BLS). Studies of the molecular defects underlying BLS have been pivotal for characterization of the regulatory system controlling the transcription of MHC-II genes. The precisely controlled pattern of MHC-II gene expression is achieved by a very peculiar and highly specialized molecular machinery that involves the interplay between ubiquitous DNA-binding transcription factors and a highly unusual, tightly regulated, non-DNA-binding coactivator called the MHC class II transactivator (CIITA). CIITA single handedly coordinates practically all aspects of MHC-II gene regulation and has therefore been dubbed the master controller of MHC-II expression. Several of the unusual features of the MHC-II regulatory system may be a consequence of the fact that CIITA originated from an ancient family of cytoplasmic proteins involved in inflammation and innate immunity. The function of CIITA in transcriptional regulation of MHC-II genes could thus be a recent acquisition by an ancestral protein having a role in an unrelated system.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Gene Expression Regulation*
  • Genes, MHC Class II*
  • Humans
  • Immunologic Deficiency Syndromes / genetics*
  • Models, Immunological
  • Trans-Activators
  • Transcription Factors


  • Trans-Activators
  • Transcription Factors