Adaptive Immunity Flashcards
What are the main 3 types of lymphocyte which come from the same precursor cell?
Natural killer cells
T cells
B cells
What is an antigen?
An antigen is a unique part of a pathogen
-antigens are what lymphocytes recognize to mount an immune response
What are the primary lymphoid organs and what is their role?
Bone marrow, and thymus
-the sites of lymphocyte development and maturation from bone marrow-derived stem cells
What are the secondary lymphoid organs and what is their role?
Lymph nodes, spleen, mucosa-associated lymphoid tissues (MALT)
-the site where immune responses are coordinated
Where are B-cells produced and matured?
Produced and matured in the bone marrow
What are the function of B cells?
Express a receptor which binds to a specific antigen
-binding to an antigen produces proliferation, maturation and production of soluble receptors called Antibodies
Where are T-cells produced and matured?
Produced in bone marrow but mature in the thymus
What are the 3 different types of T cells?
Cytotoxic T cell
Helper T cell
Regulatory T cell
What is the function of a T cell?
Express a receptor that binds to a specific antigen -Can have one of 3 outcomes Cytotoxicity Help of other immune cells Regulation (turning off immunity)
How does a lymphocyte respond differently to different antigens?
Each individual lymphoctye has a different T cell or B cell receptor which binds to a different antigen. Means each cell will respond to a certain pathogen and the immune response can be tailored for that pathogen
How are different T and B cell receptors made?
TCR gene= T cell receptor gene
BCR gene= B cell receptor gene
The TCR and BCR genes are chopped up into segments and stuck back together in different orders to make different receptors
What is the difference between antigens B and T cells bind to?
B cells bind directly to an antigen even if it’s still attached to a pathogen
T cells bind to antigens that have been chopped up and presented to them by antigen-presenting cells
What 3 signals do T cells need to be activated?
- T cell receptors binding to a specific antigen presented by major histocompatibility complex (MHC) molecules
- Costimulation (B7 family molecules)
- Cytokines (interleukins 4,10,12,23)
What does MHC stand for?
Major histocompatibility complex
What are the 2 types of antigen presentation?
MCH I
MCH II
Describe MCH 1 antigen presentation
- Infection of body cell by virus
- Virus is chopped up by the proteosome
- Antigens loaded onto the MCH I in the endoplasmic reticulum
- Activates CD8+ cytotoxic T cells
What is the function of cytotoxic T cells?
Kill the cells expressing MCH I and foreign antigen by:
- Perforin
- Interaction of Fas with Fas-ligand on the infected cell
Describe the process of cytotoxic T cell killing with perforin
- T cell binds to antigen presented by MHC I
- Adhesion molecules such as LFA-1 bind the T cell to the target cell
- Perforin released forming a cyclindrical pore in the infected cell
- Granzymes released and enter target cell
- T cell detaches
- Target cell dies from apoptosis
Describe the process of cytotoxic T cell killing using the Fas-Fas ligand
- Fas ligand is on T cells
- Fas is on target cell
- Fas ligand-Fas interaction activates FADD which activates caspase 8
- Activated caspase 8 activates caspase 3
- Caspase 3 causes the target cell to die via apoptosis
What is the difference between normal antigen-presenting cells (APC’s) and professional ones?
- All cells can present antigen to CD8+ cytotoxic T cells on MHC I molecules
- Only professional antigen presenting cells can present antigen to CD4+ helper T cells on MCH II molecules
-Professional cells express MCH II, costimulatory molecules and cytokines to give all 3 signals
Which cells are professional antigen presenting cells (APC’s) ?
Dendritic cells are the best antigen presenting cells
-Macrophages and B cells do it to
Describe the process of MCH II antigen presentation?
- Phagocytosis of pathgen by antigen presenting cells
- Pathogen is chopped up by phagolysosomes enzymes
- Antigens are loaded onto the MCH II in the phagolysosome
- Activates CD4+ helper T cells
What is cross-presentation of dendritic cells?
Cross presentation of dendritic cells is how dendritic cells can also present antigens on the MCH I molecule, meaning they can activate both helper and cytotoxic T cells
Describe the costimulation signal needed to activate T cells
B7 family molecules activate CD28 on T cells
-boosts the strength of the activation signal
