Exam 2: Dr. Pinchuk MHC Flashcards
What is the major histocompatibility complex?
MHC molecules and other proteins involved in antigen processing and presentation encoded in a cluster of closely linked genes
What was MHC first recognized as?
The site of genes that cause T cells to reject tissues transplanted from unrelated donors and recipients
Why can MHC not recombine?
It is germline encoded
What is MHC called in humans?
Human leukocyte antigen complex (HLA)
What are isotypes?
Products of the different MHC 1 and 2 genes
What are alleles?
The different forms of any given gene
What are allotypes?
Different products of any given gene
Which has a smaller diversity, MHC or TCR?
MHC
What are the 2 components of MHC diversity?
Multiple gene families
Genetic polymorphism
How many isotypes of MHC I do you have?
12: 6 from your mother and 6 from your father
What is a heterozygous individual?
Individual that inherited 2 different forms of the gene from parents
What is a homozygous individual?
Individual that inherited the same forms of the gene from parents
What is the HLA haplotype?
The particular combination of HLA alleles found on a given chromosome 6
What is HLA type?
The combination of all HLA alleles a person has
What is MHC like in each animal?
Similar, but they have a different genetic structure
Look at pictures of MHC class I and II structures
Look at pictures of MHC class I and II structures
What must T cells recognize?
A specific antigen with the correct combination with HLA
Look at MHC restriction
Look at MHC restriction
What is a significant difference between survivors and fatalities when an infectious disease strikes a population?
The complement of MHC molecules present in each individual
What does species-wide MHC polymorphism do?
Reduce the likelihood that a single infectious agent will destroy and entire population of animals
What are the advantages to multiple MHC genes that arise from balancing selection?
Contribute different peptide-binding specificities
A greater number of pathogen-derived peptides is presented during any infection
The strength of the immune response against the pathogen is improved by increasing the number of activated pathogen-specific T cells
Ensures that most members of the population are heterozygotes
What does balancing selection provide?
Polymorphism of MHC genes and molecules
What is directional selection?
Favors certain MHC alleles at the expense of others and is imposed by specific, epidemic disease
Replaces older alleles with newer variants
What is the outcome of directional selection?
Change, not balance
When does directional selection happen?
After infectious diseases
What causes people to have AIDS?
Presenting antibody to HIV
Look at HIV graph
Look at HIV graph
Which T cell chains are MHC restricted?
Alpha and beta
What MHC classes do all animals studied have?
1, 2, and 3
In general, how are MHC classes II and III described? What does it mean?
Orthologus
Derived from a single ancestor and have not been subjected to major rearrangements during evolution
How is MHC class I described? What does it mean?
Paralogous
They have been reorganized multiple times and it is very difficult to compare them in different species
Overall, what is the structure and function go MHC molecules like in domestic mammals?
They do not differ significantly
