Feb. 12th (Exam 2) Flashcards
Are natural killer cells only used in the innate immune system?
No, they have some uses in the adaptive immune system as well, but much of that is being elucidated in research.
We talked a lot about how the adaptive immune system has the ability to improve itself during the course of fighting an infection, unlike the innate immune system which has the same constant response over the course of response.
What, in large part, is responsible for this pivoting?
antibodies
Define immunoglobulin.
Immunoglobulins are the cell surface B-cell antigen receptors and the secreted antibodies.
What are the five different isotypes of immunoglobulins?
What distinguishes them?
- IgA
- IgD
- IgM
- IgG
- IgE
Their constant regions vary.
How does a mature B cell express immunoglobulin before it encounters antigen?
What is the purpose of this?
What happens (generally) once the antigen binds?
What is the single effector function of B lymphocytes?
Before the mature B-cell encounters an antigen, it only expresses immunoglobulin in the membrane bound form.
This serves essentially as the receptor for antigen on the mature B-cell.
Only when antigen binds to this receptor do we see the B-cell become stimulated to proliferate and to differentiate into plasma cells.
Plasma cells then secrete large amounts of antibodies with the same exact specificity as the membrane bound immunoglobulin.
Antibody production.
Define antibody.
How can antibodies function, in part, like C3b?
An antibody is the secreted form of a B-cell immunoglobulin.
Particular antibodies can attract other parts of the immune system with their constant regions.
What is the chief function of antibodies?
- bind antigens
- deliver antigen to other immune components.
Where can we find antibodies?
We find them in the blood, the lymph and are always present at mucosal surfaces.
How are PRRs different than antibodies?
PRRs recognize patterns that are common to many different pathogens.
Antibodies recognize things that are much more specific.
What is the antibody repertoire?
How high can it be?
What is the practical number in most people given their number of B-cells?
This is the total number of different, specific antibodies that can be made by an individual.
10^16
10^9
What are plasma cells?
They are the effector B lymphocytes that secrete antibodies.
Describe the makeup of an antibody as it relates to its protein structure.
Antibodies are glycoproteins that consist of four polypeptide chains.
2 identical light chains that each contribute 25kD
2 identical heavy chains that contribute 50 kD each
Describe the composition of each arm of an antibody in reference to its protein structure.
Each arm of the Y is made up of a complete light chain paired with the amino-terminal part of a heavy chain, covalently bonded by a disulfide bond.
Describe the composition of the stem of an antibody in reference to its protein structure.
The stem of the Y consists of the paired carboxy-terminal portions of the two heavy chains, lined by a disulfide bond.
What is the variable region of an antibody?
Answer this question in regards to its specificity.
The variable regions are the N terminal areas of the light and the heavy chains.
These areas will have heavily varied amino acid sequences between different antibodies.
What is the antigen binding region of an antibody?
How many antigen binding regions does each antibody have?
Are they different within the same antibody?
This is the combination of two variable regions, one from light and one from the heavy chain.
There are two identical antigen binding sites at each end of the Y of an antibody.
What are the constant regions of an antibody?
This is the rest of the light and heavy chains of the antibody that has little variation in the amino acid sequence between different immunoglobulin classes.
How do we get the hinge region of the antibody?
What is the purpose of this hinge?
This is the relatively unstructured part of the heavy chain.
The hinge region allows the Fabs regions to take on different spatial orientations with respect to each other.
This enables antibodies to bind antigens that are spaced out in different distances to be bound tightly by both Fab arms.
What would a protease do to an antibody?
What is the Fab region?
What is the Fc region?
A protease could be used to cut the antibody at the hinge region, leaving two Fab and one Fc fragments.
Fab region - Fragment antigen binding
Fc region - Fragment crystallizable
What does the Fab bind?
What does the Fc bind?
Fab binds antigen
Fc has the effector function of binding to serum proteins and cell-surface receptors.
What determines the isotype of each antibody?
The constant region of the heavy chains.
