THE ADAPTIVE IMMUNE SYSTEM Flashcards
How does the adaptive immune system’s response differ the most from the innate immune system’s response to infection?
The adaptive immune system targets specific antigens and produces a highly specified response
What is an antigen?
A foreign molecule that binds to T cell receptors or antibodies
Why are memory cells essential to the host’s immunity - in general?
Memory cells help the host remember an antigen if the pathogen were to reinfect
How do some pathogens bypass memory cells in the adaptive immune system?
They change their antigens with each infection, preventing memory cells from recognizing the pathogen with every reinfection.
What is the main reason activated macrophages have to regulated?
Oxidative bursts triggered by activated macrophages are extremely harmful to surrounding tissue in the host. If macrophages are not regulated it can do serious damage.
What structure do antibodies have? Explain the two main parts of an antibody:
Antibodies are Y-shaped molecules that contain a single Fc or constant region and 2 identical Fab or variable regions
What are two functions of the Fc region on an antibody?
The constant region allows antibodies to bind to C1 proteins and bind to Fc receptors on macrophages.
- C1proteins activate the complement system on the surface of bacteria
- Fc receptors trigger opsonization and alert macrophages
What is an epitope?
An epitope is a portion of an antigen that can be targeted by an antibody
How is antibody-antigen specificity exemplified by epitopes?
Antigens can have multiple of the same epitope which can be targeted by a single antibody
What is an advantage of an antibody being able to target several epitopes?
If an antigen has several peptide repeats (epitopes) it gives the antibody multiple areas to bind
What is a good indication that an antibody is working?
The activation of more B cells indicates that the antibody is targeting the right epitopes and effectively killing the pathogen
What are the 4 main types of antibodies? Provide one identifiable factor for each.
- IgG is the most widely released antibody in the body.
- IgM is the first antibody to be released and can perform bacterial agglutination
- sIgA are antibodies that can be secreted outside the body in the form of fluids
- IgE are antibodies associated with parasitic infection and allergies
What part of the antibody differs between the 4 antibody types?
The Fc region
What is affinity?
The strength by which an antigen binds to the Fab portion of an antibody
What is avidity?
Affinity coupled with valence - how many binding sites are available for the antigen and how strong the antigen binds to the antibody.
Which has a higher avidity; IgM or IgG?
IgM has a higher avidity because its structure allows for a total of 10 binding sites. IgG only has two binding sites. The affinity of both are equal, so valence determines which has a higher avidity.
B cells with the highest …… will proliferate?
Affinity
What are the two most useful functions of antibodies?
- trapping bacteria
- neutralizing bacteria
Most antibodies can neutralize antigens. What can IgM do that the other antibodies can not do?
IgM can complete bacterial agglutination
What is bacterial agglutination and why is it useful to the host?
Bacterial agglutination is a strategy performed by IgM that traps multiple bacteria in a mesh.
The mesh prevents bacteria from moving further into the host, and can be placed into mucus for further immobilization
What allows IgM to agglutinate bacteria?
It has multiple binding sites (10) that hold bacteria in the mesh.
What two antibodies can activate the complement system?
IgM and IgG
Why is IgM the first antibody to be released during a new infection?
Because it is able to capture and eliminate a lot of pathogens at once
What are two reasons why IgG is the most widely spread antibody, and most useful for sustained infection?
Because it is able to opsonize, or flag down, macrophages in order to phagocytose the pathogen. It can also cross the placenta, providing immunity/protection to the fetus if its mother is infected.
What is the vaccine given to patients that are infected with C. dipthariae
Diptheria toxoid
What does bacteria C. dipthariae attack in the body?
It kills upper respiratory mucosal cells
What allows sIgA to be secreted through mucosa?
The Fc portion of sIgA binds to mucin
What cells do IgE antibodies bind to?
Mast cells
What is the ideal response of IgE binding to mast cells? What kind of infection causes this response?
Mast cells release histamine which trigger vasodilatation and recruit macrophages that phagocytose the antigen.
Parasitic infections are best targeted by IgE.
What is a response caused by IgE binding to mast cells that is NOT ideal?
When IgE is triggered by an allergen, histamine is released and vasodilatation is triggered for a pathogen that is not harmful to the body. It is an unnecessary response
What reaction is the non-ideal response of IgE and mast cells most commonly associated with?
Allergic reaction
What specific cells recognize antigens? What does the acronym for these cells stand for?
APCs = Antigen Presenting Cells.
B cells, macrophages and dendritic cells are APCs
What molecules are used to present antigens to T cells? What differentiates the two?
Major Histocompatibility Complexes
MHC1 can be produced by any cells while MHC2 is only produced by APCs.
What is the main goal of the lymphatic system?
To prevent fluid build up in the tissues, and to replenish blood proteins and immune cells to vessels.
What are the function of lymph nodes in the lymphatic system?
Lymph nodes are like filters for the lymphatic system and capture possible pathogens/PAMPs as they pass through the lymphatic system
What cells are present in the lymph nodes?
Macrophages, B cells, DC cells and T cells
