Sara - Major Histocompatibility Intro and Structure Flashcards
What is the MHC called in humans?
Human leukocyte antigen
Where is the human leukocyte antigen gene located?
The short arm of chromosome 6
How many classes of MHC are there?
Three
Which classes of MHC are involved in antigen presentation?
Class I and Class II
In the HLA region, where is the class I region?
Class I is nearest to the telomere
In the HLA region, where is the class II region?
Class II is nearest the centromere
In the HLA region, where is the class III region?
Between Class I and Class II
What type of genes are class I and class II, how can they be described?
As highly polymorphic genes
What are non-polymorphic genes?
Genes represented by only one normal nucleic acid sequence
What are polymorphic genes?
Genes where the nucleic acid sequence varies at a relatively high frequency among normal individuals within a population
i.e. there are many different alleles that exist within the population
What are alleles?
Each common variant of a polymorphic gene present in the population
What cells express MHC Class I?
All nucleated cells
What cells express MHC Class II?
Antigen presentating cells
What are the three regions of MHC Class I region?
HLA-A
HLA-B
HLA-C regions
What does the HLA-A, HLA-B, HLA-C region code for in humans?
The A, B and C molecules of MHC Class I
What regions are responsible for Class II in the HLA region?
HLA-DP
HLA-DQ
HLA-DR
What does the HLA-DP, HLA-DQ and HLA-DR regions code for?
DP, DQ and DR molecules of class II MHC
Class I activate which cells?
CD8+ T lymphocytes (cytotoxic T cells)
Class II activate which cells?
CD4+ T lymphocytes (helper cells)
What is a MHC haplotype?
The total set of MHC alleles present on each chromsomes
What is a MHC haplotype?
The total set of MHC alleles present on each chromosome
How many MHC haplotypes does an individual have?
One from the mother and one from the father
MHC molecules are part of what family?
Immunoglobulin superfamily
What is the MHC groove cleft composed of in Class I?
(2)
Protein structure
2 alpha helical sides
A base of 8 anti-parallel B-pleated sheets
What are the four subunits of MHC class I?
a1
a2
a3
B2-microglobulin
What two chains make up the MHC class I?
an alpha chain (with three subunits)
A B2 microglobulin
What alpha chain subunits form the groove of MHC class I?
a1 and a2
How is the B2-microglobulin attached?
It interacts non-covalently with the a chain and has no direct attachment to the cell
What are the four regions of class I MHC?
An amino terminal extracellular peptide-binding region (groove/cleft)
An extracellular immunoglobulin-like region
A transmembrane region
A cytoplasmic region
What are the two chains of MHC Class II?
a chain
B chain
What are the subunits of MHC Class II?
a1
a2
B1
B2
What are the four regions of the MHC Class II?
An amino terminal extracellular peptide-binding region - groove/cleft
An extracellular immunoglobulin-like region
A transmembrane region
A cytoplasmic region
