Lecture 7 Flashcards
What is the MHC?
Set of closely linked genetic loci that are overwhelmingly important in determining fate of gengrafted tissue
Is MHC polymorphic?
Highly
Main function of MHC?
Presenting peptide to T lymphocytes
What is HLA?
Tightly linked gene cluster of cell surface glycoproteins
Regulate immune cell interactions
Evoke allograft rejections
What does HLA stand for?
Human leukocyte antigen
What are the class I loci?
HLA
HLAB
HLAC
Class II Loci?
HLADP
HLADQ
HLADR
Where are class I loci found?
Surface of nearly all nucleated cells presenting antigen to CD8+ T cells
Where are class II loci found?
DCs
B lymphocytes
Macs
Present to CD4+
What presents to CD?
Class I
What presents to CD4?
Class II
What are class III loci?
Reside in MHC region but no involved in antigen presentation
Where is the HHLA complex found?
Short arm chromosome VI
What do class I molecules associate with?
Beta2 microglobin in cell membranes?
Where in MHC is B2microglobin coded for?
Not in MHC, on different chromosome
What is B2microglobin?
Lighter chain on cell surface that associates with class I molecule
Structure of Class I?
Alpha chain
Class I polypeptide
B2microglobin
What type of bond does MHC form with antigen?
Non covalent
What varies amongst MHC molecules?
The alpha chain - varies in aa sequence
B2 microglobin is same in them all
What portion of MHC crosses cell membrane?
C terminus
What is class II molecule made of?
Alpha chain - 34k daltons
Beta chain - 29k daltons
What does MHC I bind?
Short peptides 8 - 10 aa in length
What does MHC class II bind?
13 - 17 aa peptides
Where are MHCII alpha/beta and I alpha chains coded for?
Different genens on MHC locus
Same chromosome
How are MHC genes expressed?
Co dominant manner Each person has 3 maternal and 3 paternal class 1 types Also has 3 maternal and 3 paternal II types
What does T cell response depend on?
Recognition of presented antigen
Recognition of the MHC it is presented in
What is CD8+ specific for?
Antigen in MHCI
What is CD4+ specific for?
Antigen in MHCII
What is MHC restriction?
Refers to T cells being specific for both antigen AND mhc that presents it
What are some APCs?
Macs
DCs
B lymphocytes
What does cytotoxic T cell do when recognizes MHCI and peptide?
Kills cell
What is HLA?
Major histocompatability complex for humans
Would MHC be the same in identical twins?
Likely not, highly polymorphic
How many polypeptide chains in class I?
1
How many polypeptide chains in class II?
2
What domain is antigen binding to?
Alpha 1 & 2 helixes
What are anchor residues?
Highly conserved areas on antigen allowing it to bind to certain MHCI
Can MHC bind one or many peptides?
Many
How is MHC inherited?
Strictly mendalian
Men or women better organ donors?
Women, men have some protein women don?t
How many MHC on a cell surface?
5k
What can MHC convey to a person?
Genetic survival advantage
What are T cells recognizing I MHC?
Non polymorphic region