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Critical Reviews™ in Immunology

Impact factor: 3.698

ISSN Print: 1040-8401
ISSN Online: 2162-6472

Critical Reviews™ in Immunology

DOI: 10.1615/CritRevImmunol.v16.i3.40
pages 311-330

Regulation of Class II MHC Expression

Wolfgang M. Rohn
Departments of Physiology and Biophysics University of Alabama at Birmingham, Birmingham, AL 35294-0005
Yi-Ju Lee
Departments of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294-0005
Etty N Benveniste
Departments of Physiology and Biophysics and Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294-0005

ABSTRACT

The class II genes of the major histocompatibility complex (MHC) encode the α/β heterodimeric glycoproteins that play a critical role in the induction of immune responses through presentation of processed antigen to CD4+ T lymphocytes. The constitutive expression of class II MHC antigens is restricted primarily to B cells, dendritic cells, thymic epithelium, and macrophages, although a wide variety of other cell types can be induced to express class II antigens after exposure to cytokines. The appropriate constitutive and inducible expression of class II MHC antigens is essential for normal immune function; thus, it is not surprising that aberrant expression on cell types normally class II MHC negative has been correlated with various autoimmune disorders, and lack of expression results in a severe combined immunodeficiency disorder called bare lymphocyte syndrome (BLS). In this review, we discuss the agents that both induce and inhibit class II MHC expression, the function of class II MHC antigens with an emphasis on the ability of these proteins to act as signal transducing molecules, and the molecular regulation of class II MHC expression.