Publication: Estudio del polimorfismo del gen inmunosupresor HLA-G, en amerindios
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2018-03-21
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Universidad Complutense de Madrid
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Abstract
El complejo mayor de histocompatibilidad (MHC, del inglés Major Histocompatibility Complex), constituye un conjunto de genes, en su mayoría altamente polimórficos, cuyos productos se expresan en la superficie de gran variedad de células y que son responsables de la respuesta inmune “adaptativa”. Se considera que estos genes están presentes en todos los vertebrados. Estas moléculas son glicoproteínas de membrana, que actúan como presentadoras de antígeno a los linfocitos T. Se han definido clásicamente como antígenos de trasplante, ya que median las reacciones de rechazo que se producen contra los injertos de órganos. El sistema principal de histocompatibilidad del hombre se denomina sistema HLA (del inglés, Human Leukocyte Antigen). Se localiza físicamente en el brazo corto del cromosoma 6 humano, ocupando una región de aproximadamente 4 millones de pares de bases (4Mb). La función principal de las moléculas HLA es facilitar el despliegue de fragmentos moleculares únicos en la superficie de las células, en un orden que permite su identificación mediante efectores inmunes, como los Linfocitos T. las moléculas HLA de clase I y clase II son glicoproteínas de membrana responsables de los pasos de reconocimiento y unión, mientras que otros genes de esta región, contribuyen en el procesamiento y presentación antigénico de otra forma. Un gen polimórfico es aquel que tiene una alta frecuencia de variantes genéticos, y los genes HLA son los más polimórficos de la especie humana. Esto se debe a su principal papel en la respuesta inmune...
The Major Histocompatibility Complex (MHC) is a set of cell surface glycoproteins molecules encoded by a large gene family which controls a major part of the immune system in all vertebrates. The MHC determines compatibility of donors for organ transplant, as well as one's susceptibility to an autoimmune disease via cross reacting immunization. The Human Leukocyte Antigen (HLA) is the name for the human MHC. The HLA is an extended region of the genome that spans some 4 million base pairs (bp) on the short arm of human chromosome 6 between 6p21.3. The major function of the HLA molecules is to facilitate the display of unique molecular fragments on the surface of cells in an arrangement that permits their recognition by immune effectors such as T-lymphocytes. The HLA-I or HLA-II molecules are those cell surface glycoproteins that actually perform the binding and recognition steps, while other genes that map to these regions may contribute to antigen-processing and presentation functions in other distinct ways. A polymorphic locus or gene is one that has a high frequency of genetic variants and the HLA genes are the most polymorphic genes in man. This is understandable in light of the central role these play in the immune response. HLA-I and HLA-II are not only two distinct genetic regions within the HLA system, with the HLA-III region interspersed between them, but also code for structurally different proteins. HLA-I molecules consist of a heavy chain (α chain), which is non-covalently assembled with a light chain known as β2-microglobulin (β2-m, encoded by the b2m gene on chromosome 15). HLA-II molecules are also heterodimers, composed of an α chain noncovalently assembled with a β2-m chain. Both HLA-I and HLA-II proteins have similar structure consisting of extra cellular region, trans-membrane region and a short intra-cytoplasmic tail. Class-I protein has three domains (α1, α2 and α3) of which the membrane distal α1 and α2 domains form the antigen-binding groove. The α3 domain along with β2-m form the membrane proximal region. The α and β chains of class-II have two domains each and the membrane distal α1 and β1 domains form the peptide groove while α2 and β2-m are membrane proximal regions...
The Major Histocompatibility Complex (MHC) is a set of cell surface glycoproteins molecules encoded by a large gene family which controls a major part of the immune system in all vertebrates. The MHC determines compatibility of donors for organ transplant, as well as one's susceptibility to an autoimmune disease via cross reacting immunization. The Human Leukocyte Antigen (HLA) is the name for the human MHC. The HLA is an extended region of the genome that spans some 4 million base pairs (bp) on the short arm of human chromosome 6 between 6p21.3. The major function of the HLA molecules is to facilitate the display of unique molecular fragments on the surface of cells in an arrangement that permits their recognition by immune effectors such as T-lymphocytes. The HLA-I or HLA-II molecules are those cell surface glycoproteins that actually perform the binding and recognition steps, while other genes that map to these regions may contribute to antigen-processing and presentation functions in other distinct ways. A polymorphic locus or gene is one that has a high frequency of genetic variants and the HLA genes are the most polymorphic genes in man. This is understandable in light of the central role these play in the immune response. HLA-I and HLA-II are not only two distinct genetic regions within the HLA system, with the HLA-III region interspersed between them, but also code for structurally different proteins. HLA-I molecules consist of a heavy chain (α chain), which is non-covalently assembled with a light chain known as β2-microglobulin (β2-m, encoded by the b2m gene on chromosome 15). HLA-II molecules are also heterodimers, composed of an α chain noncovalently assembled with a β2-m chain. Both HLA-I and HLA-II proteins have similar structure consisting of extra cellular region, trans-membrane region and a short intra-cytoplasmic tail. Class-I protein has three domains (α1, α2 and α3) of which the membrane distal α1 and α2 domains form the antigen-binding groove. The α3 domain along with β2-m form the membrane proximal region. The α and β chains of class-II have two domains each and the membrane distal α1 and β1 domains form the peptide groove while α2 and β2-m are membrane proximal regions...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Medicina, Departamento de Microbiología I, leída el 05-04-2017