1.3 Adaptive Immunity Flashcards
Characteristics of adaptive immunity
- Slow response
- Recognizes unlimited structures
- Improves with time
Steps for initiation of adaptive immune response
- Pathogens on epithelium
- Pathogens enter skin
- Macrophages and neutrophils start eating bacteria and produce cytokines
- Dendritic cell picks up antigen and runs to lymphocite
- Dendritic cell has interaction with B and T cells and antibodies are released into blood
Structure of B-cell receptor (surface immunoglobin)
2 light chains with heavy chain
Antigen binding site
What is this?
Structure of Antibody
Structure of T cell receptor
Alpha and beta chain and anchored to T cell
Define epitopes
Site at which unique antibodies can bind
- an antigen can have multiple epitopes where an antibody can bind
Process for genetic rearrangements
- Germline configuration (V1, V2, J1, and J2 are separated)
- Somatic recombination (unique V regions are combined with unique J regions)
- Rearranged gene (excised DNA is chopped out and VJ genes are pasted together
Progenitor cells give rise to
Large number of lymphocytes (B and T cells)
Describe clonal selection
Pathogen reactive lymphocytes created are triggered to divide and proliferate and pathogen activated lymphocytes differentiate into effector cells that can eliminate pathogen
Steps for B cell removing toxins
- Toxins released into body by pathogens and interact with host receptor
- Antibodies form a latice network with toxin and neutralize it
- Tail of antibody interacts with receptor on cell
- Endocytosis and degradation of antibody toxin complex
Steps for B cell uptake of pathogens
- Bacteria in extracellular space
- Antibodies bind to bacteria (opsonization) OR some antibodies surround bacteria + complement
- Antibody tail interacts with receptor on cell OR antibody + complement binds to receptor of complement
- Ingestion and destruction of phagocyte
Class specific binding
Class of antibody refers to the heavy chain constant region
Ex: IgM and IgG
What is the first antibody class made against an infecting pathogen?
IgM
___ selects for antibodies that bind more tightly to the pathogen
Somatic hypermutation
T cells regulate the ___
Immune response
- How it goes up and down and what’s done
How do T cells function?
Make contact with other cells and induce them to change
Steps when CD8 T cell is involved
- CD8 T cell interacts with receptor on surface of viral infected cell
- Stimulates CD8 to induce apoptosis
What are the 2 scenarios for when a CD4 T cell is involved?
Scenario 1:
- CD4 T cell recognizes receptor on surface of macrophage
- Interaction produces cytokines
- Cytokines activate macrophage and it does a respiratory burst to chew up bacteria and produce cytokines
Scenario 2:
- CD4 T cell interacts with a B cell receptor
- Produces cytokines
- B cell now becomes plasma cell and secretes antibodies
Describe dendritic cells
- A type of macrophage
- Exists under surface of skin or mucosal layers
- Grabs invaders in body and carries them to lymph node to see if they can find a T or B cell to interact with
Steps for antigen presentation by the dendritic cell to the T-cells
- Dendritic cell takes up pathogen
- Travels to lymph node, and pathogen is taken apart in dendritic cell
- Pathogen proteins are cut into small peptides
- Peptides bind to MHC molecules and complex goes to surface of dendritic cell
- T-cell receptors bind to peptide:MHC complex on dendritic surface
MHC molecules are involved in ___ recognition
Antigen
MHC class I coreceptor
CD8
MHC class II coreceptor
CD4
Steps for MHC II protecting against antigens and activating macrophages:
- Macrophage engulfs bacteria and produces peptides
- Peptides bind to MHC class II
- Transported by MHC class II to cell surface
- Helper T cells recognize complex and activates macrophage
Steps for MHC II protecting against antigens and activating B cells:
- Antibodies (cell surface immunoglobins) bind to bacteria, it’s engulfed into B cell and peptides are produced
- Peptides bind to MHC class II
- MHC class II transports complex to B cell surface
- Helper T cells recognize complex and activates B cells
Where are MHC I molecules found?
Most cells within the body, EXCEPT RBC
Where are MHC II molecules found?
Only B-cells, macrophages, and dendritic cells
- All antigen presenting cells (APCs)
Can mature T cells be only CD4 or CD8, or can they be both?
Not both, only 1
Steps for MHC I protecting against intracellular antigens:
- Virus infects cell
- Viral proteins are made in cytoplasm
- Peptide fragments of protein are bound to MHC I in ER
- Complex is transported by MHC class I to cell surface
- Cytotoxic T cells recognize complex and kill infected cell
Steps for clonal selection with T-cell self antigens:
- Hemapoetic stem cells in the bone marrow produce immature T cells
- Immature T cells are released into blood and go to thymus
- T cells are positively selected for MHC markers on cell surface
- The ones w/o correct marker go to thymus and interact with cortex and fade away AND cells with correct marker are positively selected and stimulated to divide
- T cells interact with thymic medulla
- If pos. selected cells are interacting, binding and recognizing self antigens, then those cells die and are negatively selected
- Those that survive negative selection leave the thymus for circulation
Steps for of unwanted adaptive immunity response in childhood virus:
- Immune response reacting to viral infection and makes Tc cells
- T cell may react with MHC:peptide complex on the surface of healthy B cells
- Activated T cells attack and kill pancreatic B cells
How does pollen trigger an unwanted adaptive immunity response?
Produces symptoms of respiratory infection through IgE of mast cells
