MHC Flashcards
Where is the human major histocompatibility complex (HLA) located?
short arm of chromosome 6
What are the subsets of the MHC class II molecules?
HLA-DP, HLA-DQ, and HLA-DR
Describe what it means to have co-dominant expression of MHC alleles.
Each individual expresses 3 maternal and 3 paternal class I MHC types, as well as 3 maternal and 3 paternal class II MHC types (on cells that express class I and class II)
The MHC is a set of closely linked genetic loci (genes of MHC) found to be overwhelmingly important in what?
determining the fate of engrafted tissue
Why do we want to minimize use of immunosuppressive therapy post-transplantation?
Immunosuppressive therapies often suppress the overall immune system, which is what we want to avoid in transplant patients.
Are MHC molecules exactly the same in identical twins?
Yes, this is why an identical twin is an ideal donor.
Which part of the MHC confers polymorphism?
the peptide binding groove (b/t alpha 1 and 2 in class I, and b/t alpha 1 and beta 1 in class II)
Cytotoxic T lymphocytes (CD8+) are specific for foreign antigen plus ________, whereas T helper lymphocytes (CD4+) are specific for foreign antigen plus ________.
products of class I loci; products of class II loci
What is MHC restriction?
Foreign antigens are restricted by the MHC molecule that’s presenting them, as T-cells have a specific reactivity on foreign antigen PLUS MHC products, rather than the foreign antigen alone.
(rephrase: a T-cell recognizes a particular foreign antigen in the context of 2 alpha helices of a particular MHC molecule)
What does it mean for MHC genes to be polymorphic?
There are many different alleles in the different individuals within a population.
How does MHC polymorphism contribute to transplant rejection?
Because MHC variation is high in the human population and there are so many alleles for each HLA gene, any two individuals who are not identical will express differing MHC molecules.
Cytotoxic T lymphocytes are elicited by what?
host cells that carry foreign antigens (ex: virus-infected cells)
What does it mean for MHC genes to be highly polymorphic?
There are many different alleles in the different individuals within a population.
What are the MHC Class I vs. MHC Class II loci?
Class I: HLA-A, HLA-B, HLA-C
Class II: HLA-D (which includes 3 subsets - DR, DQ, DP - that are alpha and beta chains that come together to form an antigen-presenting molecule)
Which type of peptides do MHC class I vs. class II bind?
I- short peptides, ~8-10 aa’s in length
II- long peptides, ~13-17 aa’s in length
