Lecture 21 Flashcards
(29 cards)
When do T cells recognize antigens
- only when presented on specialized molecules
- they must be bound on the MHC of the APC
How do antigen and lymphocytes meet?
Secondary lymph tissue
- spleen ( blood borne antigens)
- lymph nodes
T-cell antigen presentation by dendritic cells
▪ Dendritic cell in epithelium: capture microbial antigen
▪ Activation of dendritic cells
▪ Migration to draining lymph node (chemokines)
▪ Maturation: Due to cytokines and TLR- signaling
▪ Expression of MHCII and co-stimulators for stimulation of T cells
Where would I fund the dendritic cells
They can be found in the Paracortex
Which is also where T cells can be found
Give the 3 signals of antigen recognition
Signal 1- antigen presentation
Signal 2- co stimulators signal
Signal 3 - cytokine secretion
What are MHC used for
- antigen processing
- antigen presentation
- responsible for graft rejection
What are the cluster of genes of the MHC called and break them down
HLA (human leukocyte antigen)
MHC class 11 - DP ,DQ,DR
MHC 1 - B,C,A
The alleles in MHC class II
DP,DQ,DR
The alleles In MHC I
A,B,C
The alleles in MHC III
- complement
- HSp70
- TNF
Class I MHC structure
- In the transmembrane you’ll find the alpha Chain which is encoded by A,B,C regions
- B2 micro-globulin (encoded by another gene in another chromosome )
Class II MHC structure
– α1 and α2 chain
• Transmembrane
– β1 and β2 chain
• transmembrane
Difference between where MHC I and MHC II are expressed
MHC I are expressed on the majority of nucleated cells
MHC II expressed on antigen presenting cells (APC)(macrophages ,dendritic cells , B cells )
MHC I - PEPTIDE BINDING
-▪a3, binds to CD8 on cytotoxic T cells
▪Presents an endogenously processed antigens
MHC II - PEPTIDE BINDING
▪ b2, highly conserved, binds to CD4
on helper T cells
Present Ag that are in the phagosome
which is the best professional APC and why
- Dendritic cells
- has antigen presentation to naïve T cells
who do macrophages present antigens to
-CD4 effector T cells
-
who do B lymphocytes present antigens to
-CD4 helper T cells
how are EXOGENOUS
PATHOGENS
eliminated
Eliminated with the help of: T helper cells that use antigens generated by ENDOCYTIC PROCESSING Antigens generated by endogenous and endocytic antigen processing activate different effector functions ENDOGENOUS PATHOGENS EXOGENOUS PATHOGENS Antigens presented to TH cells by MHC Class II
how are ENDOGENOUS
PATHOGENS eliminated
Killing of infected cells by CTL that
use antigens generated by
CYTOSOLIC PROCESSING
Antigens presented to Tc cells by
MHC Class I
describe the cytosolic pathway
-ubiquitin-proteins targeted for lysis combine w/ a small protein
-ubiquitin -protein complex is degraded by a proteasome
-specific proteasomes generate peptides which can bind to MHC 1
-Cytoplasmic cellular proteins, including non-self proteins
are degraded continuously by a multi-catalytic protease of 28 subunits
-The components of the proteasome are induced by IFN-y
Transporters associated with antigen processing (TAP1 & 2)
- put in the ER
- transported across ER
- to put antigens in the MHC molecule
what do immuno evasins do
• Viruses block MHC class I from properly presenting them to CD8 T cells. ✓Inhibit peptide transport ✓Inhibit peptide loading ✓Cause MHC class I degradation
what does HSV protein do
protein blocks transport
of viral peptides into
