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19 Cards in this Set
- Front
- Back
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What is the HLA gene complex?
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short arm of chromosome 6
4,100 kbp 200 loci |
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What is the Class I region of the HLA gene?
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Encodes for heavy chains of HLA-A,B,C
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What is the Class II region of the HLA gene?
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Encodes genes for alph and beta chains for HLA-DR,DQ,DP
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What are 3 levels of variation among different population?
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1. HLA alleles occur in all population, but at different frequencies
2. HLA alleles restricted to a specific population 3. Haplotypes held together through linkage disequilibrium appear to be population restricted |
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HLA molecules
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Expressed on cell membranes of many different cell types.
Constructed of more than 300 amino acids |
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What is the distribution of Class I molecules?
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Found on many, but not all nucleated cells. Also occur on platelets.
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Expression of Class II molecules
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Restricted to few cells-B cells, dendritic cells, Langherhans cells within the skin, and on some endothelial cells.
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Cytokines (Interferon)
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Initiate increased or new expression of HLA molecules
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Physical structure of HLA Class I molecule
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Contain alpha (heavy) protein chain (alpha1,2,3 domains) that is noncovalently associated with B-2 microglobulin (light) non-polymorphic protein
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Physical structure of HLA Class II molecule
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two distinct glycoprotein chains, alpha and beta
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What is an epitope or antigenic determinant?
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the minimum structural unit that can be recognized by a B or T cell receptor
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What is an alloepitope?
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epitopes that differ among individual members of the same species
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Peptide Groove
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Where serologically definble epitopes are located.
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Nonsynonymous Substitution
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substitutions of an amino acid with different biochemical characteristics (alanine-->glutamine)
are more frequent in the region of peptide groove |
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Private Epitope
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epitopes that occur on a single gene product such as HLA-A2
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Public Epitopes
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HLA antibodies that react with more than one gene product and detect crossreactive epitope
example Bw4 and Bw6 |
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Haplotype
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half of a genotype
combination of linked HLA genes transmitted on a single parental chromosome |
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Recombinant HLA haplotypes
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created during meiotic cell division of germ cells
chromosomal replication-->X shaped chiasmata-->cross over site-->complemetnary exchange of genetic material |
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Frequency of recombination
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directly related to distance between loci
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