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19 Cards in this Set

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