Flashcards in Major Histocompatability Lecture 6 Deck (19):
What are the two main types of MCH gene products?
Class 1 and class 2 molecules
What are the three types of genetic loci that make up the HLA?
Class 1, class 2, class 3
What are the loci within class 1? Where are these molecules present? What cells do they present antigen to?
Virtually all nucleated cells
Present antigen to CD8+ Tlyphocytes
What are the loci within class 2? where are these molecules present? What cells do they present antigen to?
Subset loci (DR, DQ, DP)
-these molecules are found on dendritic cells, b-lymph, and macrophages
-Present antigen to CD4+T lymphocytes
What type of cell do class 3 loci present to?
Dont present antigen to T-lymphocytes
Where is the HLA complex found?
Short arm of Chromosome 6
What does the cell surface molecule of Class 1 look like?
-1 alpha chain (class 1 polypeptide) (44,000 daltons)
-1 light chain beta2 microglobulin (specified by a gene on anothr chromasome) (12,000 daltons)
-they are associated non-covalently
What holds up the a2 and a1 chains on the MHC class 1 molecule?
B2 and a3 make up a beta pleated sheet platform
What do the two helices on the MHC class1 molecule form?
Cleft that binds antigenic peptide fragments
Which class 2 loci code for?
2 polypeptide chains
a chain (34,00 daltons)
b chain (29,00 daltons)
-alpha 1 and beta 1 make cleft
What type of peptides does MHC class 1 bind vs MHC class 2?
MHC class 1: short peptides of 8-10 aa in length
MHC class 2: longer peptides of 13-17 aa in length
Are anchor residues that bind a particular MHC class 1 molecule need to be identical? How else do peptides bind to class1 MHC molecules?
No but they are always related such as all hydrophobic.
-Also bind through their amino and carboxy termini
Are anchor residues that bind a particular MHC class 2 molecule need to be identical?
No but they are always related such as hydrophobic, negatively charged, basic aa, hydrophobic
Where do the proteins that are encoded by MHC start out then go to and as what?
associate with the ER and then shuttle to the cell surface where they are membrane glycoproteins
How are MHC antigens codominatly expressed?
each individual express 3 maternal and 3 paternal for class 1 and 3 maternal and 3 paternal for class 2
Does each individual have 2 half sets of genes both expressed equally?
What is MHC restriction?
The dependence of the T cells reactivity on
2. MHC products
rather than just the Ag alone
What do cytotoxic T lymphocytes recognize?
complex of viral peptides with MHC class 1 and kills infected cells