What Is the Major Histocompatibility Complex?
The major histocompatibility complex (MHC) is a collective term for a group of genes encoding animal major histocompatibility antigens. Human MHC is located on the short arm of human chromosome 6 and mouse MHC is located on mouse chromosome 17. The length of MHC is about 4 × 10 ^ 6bp. Human MHC is also called HLA (human leukocyte antigen, HLA) complex. MHC in mice is called the H-2 gene. Due to the polygenic nature of MHC, according to the structure, tissue distribution and functional differences of the coding molecules, it can be divided into MHC class I, MHC class II, and MHC class III genes, which encode MHC class I molecules, MHC class II molecules, and MHC III Class molecules. Human MHC products are commonly referred to as HLA (human leukocyte antigen, HLA), which is human leukocyte antigen.
Major histocompatibility complex
- The major histocompatibility complex (MHC) is a collective term for a group of genes encoding animal major histocompatibility antigens. Human MHC is located on the short arm of human chromosome 6 and mouse MHC is located on mouse chromosome 17. The length of MHC is about 4 × 10 ^ 6bp. Human MHC is also called HLA (human leukocyte antigen, HLA) complex. MHC in mice is called the H-2 gene. Due to the polygenic nature of MHC, according to the structure, tissue distribution and functional differences of the coding molecules, it can be divided into MHC class I, MHC class II, and MHC class III genes, which encode MHC class I molecules, MHC class II molecules, and MHC III Class molecules. Human MHC products are often referred to as HLA (human leukocyte antigen, HLA), that is,
- Appears during skin transplantation between different mammalian individuals
- 1. Types of MHC molecules
- Different MHC-encoded products have different functions.
- MHC class I (MHC I): It is located on the surface of general cells and can provide some conditions in general cells.
- The HLA complex is located in the short arm of chromosome 6 in the range of about 4000 kb and consists of a group of closely linked genes. The HLA complex is by far the most complex human genetic system known. From
- Gene names in HLA complex class and class gene regions
|
| ||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |
|
|
| |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
- Studies have found that many diseases do show significant correlation with certain HLA alleles or HLA haplotypes. HLA antigen-associated diseases have several characteristics that should be noted: the etiology and pathophysiology are unknown, the genetic pattern is distributed but the penetrance is weak; it is associated with immune abnormalities; and it has little or no effect on reproduction.
- Population and pedigree studies can be used to confirm the association of marker genes in the HLA complex with various disease states. Because group research is easy to carry out, most of the relevant information comes from such research. The correlation between specific diseases and certain specific HLA antigens is quantified by calculating the odds ratio (OR), which can be expressed as the risk ratio of individuals with disease-associated HLA antigens compared to individuals lacking such antigens. The higher the OR, the higher the frequency of the antigen in the patient population. Take patients with ankylosing spondylitis with HLA-B27 as an example. 90% of Caucasians with the disease in the United States have HLA-B27, and the rate of American Caucasian controls is close to 9%. OR = (90 × 91) ÷ (10 × 9) = 91. Therefore, HLA-B27-positive individuals are 91 times more likely to develop the disease than HLA-B27-negative individuals. Because the frequency of an antigen is often significantly different between races. It is necessary to compare patients and controls in the same race. For example, HLA-B27 was found in 48% of African Americans with ankylosing spondylitis, and only in 2% of African American controls.
- Many diseases have been found to be associated with certain antigens. The correlation between HLA and disease can be divided into statistically positive correlations, possible correlations, and potential correlations. The positive correlations are: ankylosing spondylitis (antigen B27), Wright's syndrome (B27), acute anterior uveitis (B27), juvenile rheumatoid arthritis (B27), celiac disease (B8) , Exophthalmic goiter (B8, DW3), myasthenia gravis (B8, DR3), herpes dermatitis (B8), chronic active hepatitis (BW6, DR8), juvenile diabetes (B8, DR3), multiple sclerosis ( B7, DR2). Possible correlations are: systemic lupus erythematosus (DR3), pemphigoid (B13), autolytic hemolytic anemia (A3), polio (A3, B7), and Behcet's disease (B5). Potentially related are: acute lymphoblastic leukemia (A2, B12), chronic glomerulonephritis (A2), leprosy (B14), Hodgkin's disease (A1, B8). [5]