Lecture 6: MHC and Ag Presentation to T cells Flashcards
in order to activate T cells Antigens in host cells are broken up into ____ peptides (processed) and displayed by MHC molecules on their surface
linear
T T cell antigen receptor (TCR) only recognizes ____ Antigens (peptides) bound to MHC molecules
linear peptides (processed)
CD4 and CD8 attach to the _____ part of the MHC class II and MHC class I molecules, respectively
non-polymorphic (non-variant)
is recognition of the peptide Ag by the TCR sufficient to activate the naive T cells
- No: co-stimulatory molecules are required together with co-receptors
Th1 cells help ___ to get rid of intracellular microbes and help the development of ______ to kill virus-infected cells
- Macrophages, CTLs
Th2 cells are mainly involved in helping _____ cells develop into ____ and ____
B cells develop into memory cells and plasma cells that produce antibodies
The TCR is composed of _______ polypeptide chains
two (most are alpha and beta but some are are gamma and delta chains)
The gamma/delta T cells have some of the characteristics of alpha/beta T cells, but have a
broader specificity for unconventional Ag such as HSPs and phospholipids
The genes coding for TCR polypeptide chains are members of the
Ig super family
The T cell receptor complex consists of the TCR, the alpha/beta or gamma/delta dimer, in association with
CD3
CD3 is a signaling complex composed of ___, ____ and ____ chains
gamma, delta, and epsilon
What are the three major class genes for Class I MHC
- HLA-A
- HLA-C
- HLA-B
- on chromosome 6
What genes are responsible for MHC class II
- HLA-DR
- HLA-DQ
- HLA-DP
- on chromosome 6
Class I MHC genes (HLA-A, HLA-B, and HLA-C) encode a polymorphic heavy chain which combines with _____ and is expressed on the surfaces of all nucleated cells
beta2-microglobulin
Class II MHC genes (HLA-D) encode molecules (HLA-DP, HLA-DR, HLA-DQ) composed of two dissimilar ____________ (an alpha and beta chain), both of which contribute to the peptide-binding groove
polymorphic polypeptide chains
MHC class I and class II are the peptide-binding domains of these molecules and bind peptides ranging from _____ and _____ amino acids residues, respectively
8-10 (MHC class I)
10-20 (MHC class II)
Class I molecules are composed of a polymorphic alpha chain non-covalently attached to the ___________
non-polymorphic Beta2-microglobulin (beta2m)
class II MHC molecules are composed of a polymorphic alpha chain non-covalently attached to a
polymorphic beta chain
source of protein antigens for Class II MHC molecules
Endosomal/lysosomal proteins (mostly internalized from extracellular environment)
Source of protein antigens for class I MHC molecules
Cytosolic proteins (mostly synthesized in the cell; may enter cytosol from phagosomes)
Site of peptide loading for MHC class II
Specialized vesicles
Site of peptide loading of MHC class I
Endoplasmic reticulum
enzymes responsible for pepide generation for MHC class II
Endosomal and lysosomal proteases (e.g. cathepsins)
Enzymes responsible for peptide generation for MHC class I
Cyoplasmic proteasome
