HLA-G

HLA-G is a Human leukocyte antigen that belongs to the HLA class I heavy chain paralogues. This gene encodes a heavy chain for the nonclassical (class Ib) major histocompatibility complex (MHC) antigen. The function of the HLA-G antigen is assumed to be involved in immune response regulation.

Structure

The HLA-G antigen is a heterodimer consisting of a heavy chain and a light chain (beta-2 microglobulin). The heavy chain is approximately 45 kDa and is anchored in the membrane. It is composed of three domains: alpha1, alpha2 and alpha3. These domains form a groove for antigenic peptide binding.

Function

HLA-G may play a role in the development of the placenta and the maternal immune response to pregnancy. The HLA-G protein has also been postulated to function in certain cell adhesion processes as well as in the regulation of T-cell and natural killer cell functions.

Clinical significance

HLA-G is unique among the class I antigens in that it possesses several primary transcript variants and can be expressed as a soluble molecule. Abnormalities in the expression of this gene have been observed in neoplasia, with higher than normal levels found in melanoma, renal cell carcinoma, ovarian cancer, and non-small cell lung cancer. Lower than normal expression has been observed in chronic hepatitis C infection.

See also

• HLA-A
• HLA-B
• HLA-C
• HLA-E
• HLA-F
• HLA-H

References

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