5.1 Adaptive Immune Response I Flashcards
Different types of APCs
Macrophages
Dendritic cells
Langerhan cells
B-lymphocytes
Dendritic cells present pathogen to what cell & function
Naive T cells
Function: T-cell response against most pathogens
Langerhans cells present pathogens to what cells & function
Naive T cells
Function: T-cell response against most pathogens
Macrophages present pathogen to what cell & function
Effector T cell
Function: Phagocytic activities
B cells present pathogen to what cell & function
Effector T cells
Function: Antibody/humoral response
Naive T cells
T cells that have not previously encountered the antigen
Effector T cells
T cells that have previously encountered the antigen and are capable of performing effector functions during an immune response
Features of APCs
Strategic location
Diversity in pathogen capture mechanisms
Diversity in pathogen sensors (PRR)
-extracellular, intracellular
Extracellular pathogens include
Bacteria
Fungi
Protozoa
Describe the exogenous pathway
- Microbes (ECM) captured via phagocytosis
- Degraded into small peptides in endsome
- Vesicles fuse with other vesicle containing MHC class II molecules
- Formation of peptide-MHC class II complex
The exogenous pathway only occurs in what type of cell?
APCs
Describe the endogenous pathway
- Viral protein present in cytoskeleton
- Marked for destruction by proteasome
- Antigenic peptide (generated by proteasome) is transported to ER where they enter through TAP1/2
- Formation of peptide-MHC class I complex
The endogenous pathway occurs in what type of cell
All cell types
What is the difference between the exogenous and endogenous pathway
Exogenous: APCs presents peptides of ECM to CD4+ T cells (class II)
Endogenous: APCs and non-APCs present peptides from ICM to CD8+ (class I)
Clinical importance of MHC molecules
- Host can deal with variety of microbes (genetic polymorphism)
- No two individual have the same set of MHC molecules
- Different susceptibilities to infections
Types of MHC class I molecules
HLA-A
HLA-B
HLA-C
Types of MHC Class II molecules
HLA-DP
HLA-DQ
HLA-DR
Role of APCs
Sense, Capture, Process, Present the pathogen
Key features of MHC molecules
- Co-dominant expression (MHC class 1 and 2 co-expressed)
- Polymorphic genes (diff. individuals present and respond to diff. microbes)
- Presentation of microbial peptides
Where are MHC class I molecules expressed
All nucleated cells
Where are MHC class II molecules expressed
APCs
Examples of APCs
Dendritic cells
Macrophages
B cells
How are microbes presented by MHC molecules
Peptide binding cleft (variable region with highly polymorphic residues)
Broad specificity (many peptides presented by the same MHC molecule)
Responsive T cells
Different HIV antigens
Cell surface proteins: gp120, gp41
Gag proteins: p24, p17, p6
What features do long-term non progressors of HIV patients have
MHC class I molecules that corresponds to the region of a virus that doesn’t mutate.
-able to attack it regardless of how many times HIV virus is mutated
Clinical conditions with MHC molecules
-Organ transplant rejection (HLA molecules mismatch between donor and recipient)
-Autoimmune disease
