Antigens and antibodies Flashcards
What are the group of chemicals (polysaccharide, protein etc) that the adaptive immune system recognizes?
Epitopes or determinants
What accounts for the adaptive immune system’s specificity?
Lymphocyte having cell membrane receptors that distinguish between epitopes
How many specificities does each lymphocyte have?
One!!
What accounts the in lowered response time of a secondary infection/immunological memory?
Immunologic memory is due to the presence of memory cells.These cells are more sensitive to stimulation by antigen than are antigen-naive lymphocytes
What are the three factors that abate the immune response?
- Removal of antigen (no further stimulation)
- Death of activated lymphocytes
- Regulatory immune system
What phospholipid is the marker for cell death?
Phosphatidyl serine on the outside of a cell membrane
How are autoimmune diseases brought about?
When immune cells that are specific for self proteins do not undergo apoptosis during development
What is immunogenicity?
The property of a molecule that allows it to induce an immune response.
What are adjuvants?
Chemicals that prolong another molecule’s (like antigen) retention in the body so that a more vigorous immune response can occur
What is antigenicity?
The property of a molecule that allows it to react with an antibody.
What are haptens?
Small molecules that cannot induce antibody formation but can react with antibody that is specific for it, (i.e. it must be coupled to a carrier molecule in order to induce antibody formation. Therefore, an hapten is an antigen, but not an immunogen).
What molecular weight is the dividing line between immunogenic and less immunogenic immunogens?
Molecules of >10,000 molecular weight are the best immunogens
The (BLANK) complex the molecule, the more capable it is to be an immunogen.
More
Where does immunogne processing occur?
In phagocytes
What are the areas of the immunogen that are easy to reach and generate a strong immune response called?
Immunodominant areas
What are the five features of immunogens that give them a strong immune response?
- Size
- Internal complexity
- Degradability
- Foreignness
- Accessibility
What are linear determinants?
Epitopes that are formed by adjacent amino acids
What are conformational determinantss/epitopes?
are composed of amino acid residues from different parts of the protein that are brought together in space.
T lymphocytes can only recognize what type of determinant (linear or conformational)?
Linear
What are neoantigens?
new antigens” formed by proteolysis, phosphorylation, or exposure of new determinants through the interaction with foreign antigens
Most antigens that the body is exposed to are of what type of chemical (polysaccharide, proteins, lipids, etc.)?
Proteins
Where are antibodies found?
- Surfaces of B lymphocytes
2. Blood plasma/tissue fluids
How many specific antibodies can any given B cells have?
Just one
What are the two types of immunoglobin that B lymphocytes contain/
IgM and IgD
B lymphocytes have both IgG and IgM immunoglobin. What, therefore, must occur if a B cell needs to produce antibodies of another isotype?
Isotope switching
Blood plasma and tissue fluids contain large amounts of antibody that has been secreted from what cell type?
Plasma cells
True or false: The antibodies produced by plasma cells have only minor changes compared to the immunoglobin that is present on the plasma cells surface
True
What immunoglobin type are found on the surfaces of mast cells? What type of antibodies do these capture?
IgE–capture soluble antibodies
True or false: Secretory fluids such as mucus and milk contain do NOT antibody
False
What is antiserum?
Antibody-containing serum.
What is serum?
the fluid portion of the blood after the cellular elements have clotted
What are polyclonal antiserums?
A population of antibodies which (collectively) can bind to more than one particular antigen, since each antibody will bind different antigens
What are monoclonal antiserums?
antiserum that contains antibodies which bind to only one specific antigen
What is an antibody titer?
the reciprocal of the last dilution of antiserum that still yields a demonstrable antibody binding reaction
What are the three bands into which antibodies separate into when undergoing electrophoresis? In which band are most found?
Alpha
Beta
Gamma–most found
True or false: the term “immunoglobin” is synonymous with “antibody”.
True
What are the two major components that antibodies are made of (hint, there are two pairs of these general structures)?
Light chains
Heavy chains
How may amino acids make up a general immunoglobin chain’s domain?
~110
What are the three genes that allow for the variability of immunoglobins?
V, D, and J
In which part of the antibody are variable regions found, heavy or light chain?
Both
Heavy chains of antibodies are connected together via what type of bond?
Disulfide between C residues
What connects the two light chains of the antibody together?
Disulfide bonds between the carboxy terminus of the light chain to the VH or CH1 region of the heavy chain
The variable regions can be subdivided into what two regions?
Hypervariable region
Framework regions
What are hypoervariable regions? How many are there?
Three areas on the heavy and light chain that come together to form the antibody binding surface.
What region provides antibodies their great variability?
Hypervariable region
What type of interactions occur at the hypervariable binding site?
Transient non-covalent interactions
What antibody types have hinge regions? What are these used for?
IgG, IgA, and IgD.
These are used to facilitate binding where there is a large space between different parts of an antigen
All five antibody isotypes can be expressed in two forms, which are what?
Secretory and membrane form
Secretory forms of IgM and IgA have what additional piece that allows the formation of pentamers of IgM and dimers or trimers of IgA?
A tail piece that allows the addition of a J chain
Which isotypes can only be secreted as monomers?
IgG, IgD, and IgE
What are the five classes of immunoglobin?
G (IgG), IgM, IgA, IgD, and IgE
Isotype switching allows a single antigen specificity to be used for different biological functions, which is provided by what?
different antibody constant regions
Papain digestion of antibodies results in what?
Two Fab chains, each having one antigen binding site, and one Fc fragment.
Pepsin digestion of antibodies results in what?
a single F(ab’)2 fragment, with two antigen binding sites, and no surviving Fc fragment.
What does the greek letter denote in the name of an antibody?
Its class, with each class mediating a different biological effect
What do the subclasses of antibodies denote?
The order of abundance in the serum
What is the antibody in highest abundance in the human body?
IgG–70%
True or false; The secretory form of IgG is a dimer
False–monomer
Which complement pathway is IgG good at activating?
The classical complement pathway
Which IgG subclass does not activate complement?
IgG4
Which IgG subclasses can opsonize microbes? What receptor on the surface of bacteria is resonsible for this?
IgG1 and IgG3
Fc receptors for IgG
What isotype of IgG can coat target cells, such as tumor cells or virus-infected cells, to facilitate antibody-dependent cell-mediated cytotoxicity (ADCC) by natural killer cells and macrophages.
IgG1 and IgG3
What is the only immunoglobulin class capable of crossing the placenta to convey protective immunity to the fetus?
IgG
Specific receptors on the placental cells attach to the what portion of the IgG molecule to actively transport the antibody through the cells and into the fetal blood circulation?
Fc portion
What immunoglobin subclass is present in breast milk?
IgG
What is the second most highly concentrated immunoglobin isotype found in the serum?
IgM
The secretory form of IgM is of what type (monomer, dimer, trimer, etc)?
Pentamer
The pentameric structure of the IgM subclass is stabilized by what structure?
The J chain
Can the IgM subclass activate complement?
Yes
Which is better at activating complement, IgG or IgM?
IgM
(1. ?) is the predominate antibody produced in a primary immune response, whereas in a secondary immune response (2. ?) is the main antibody produced.
- IgM is the predominate antibody produced in a primary immune response
- In secondary immune response IgG is the main antibody produced.
Which isotype of immunoglobin can be transported across mucosal barriers into the respiratory tract or the lumen of mucosa-lined organs (example: intestines) to neutralize microbes, etc
IgA
Receptors on respiratory or intestinal epithelial cells can bind the IgA by what region, to transport it across the membrane?
Fc receptor
Where else besides mucus is IgA present?
Tears, saliva, colostrum, and milk
IgA has what structure in its secretory form (monomer, dimer, trimer etc)? In secretions?
Monomer in serum, dimer in secretions
What type of transport brings IgA outside of the mucosa?
Vesicular transport
During the process where dimeric IgA is transported through the mucosal cells, it is coupled with what protein? What does this do?
coupled secretory piece which protects the IgA from proteolytic enzymes while in the secretions and to act as a “glue” to bind it to the mucus found at mucosal sites
Secretory piece is derived from what?
epithelial cell Fc receptor that binds IgA in order to internalize it
In the serum, the ratio of IgA1 to IgA2 is (?):(?), whereas in the gut the ratio is (?):(?).
In the serum, the ratio of IgA1 to IgA2 is 4:1, whereas in the gut the ratio is 3:2.
The IgA dimer is held together by what chain?
J-chain
What is the immunogloin isotype that is found in the second to least amount in the serum?
IgE
What structural type is IgE secreted as (monomer, dimer, etc)?
Monomer
What does IgE bind to, and mediate?
Binds to cell surface receptors for IgE on basophils and mast cells to mediate allergies and anaphylaxis
Does the IgE receptor on mast cells have a high or low affinity for IgE?
High
What does IgE faciliate eosinophils with?
ADCC of certain parasitic infections
What is the immunogloin isotype that is found in the in the samllest amount in the serum?
IgD
Where is IgD primarily found?
on the surface of antigen-unstimulated B lymphocytes, along with IgM.
What is IgD important for?
the transduction of signals across the plasma membrane to result in antigen-driven B cell activation
What happens to B cells only expressing surface IgM, when exposed to antigen?
They become tolerized and do not go on to secrete antibody.
What is affinity?
The strength of binding for antigen of one antigen combining site, i.e. one arm of an antibody.
What is affinity maturation?
The average affinity for a population of antibodies will increase with repeated immunization with an antigen.
What is avidity?
The overall strength of attachment of an antibody which takes into account how many antigen combining sites the antibody has bound. For example, IgG antibodies only have two antigen combining sites with which to bind antigen, but IgM can bind up to 10 antigen combining sites.
What are allotypes?
Differences in the constant regions of antibodies (of the same isotype) between different individuals due to the presence of multiple alleles of the constant region genes in the human population.
What are idiotypes?
The collection of hypervariable regions (formed by the rearrangement of immunoglobulin gene segments) contributed by heavy and light chains to form the antigen-binding site, i.e. idiotype is the unique features of an antigen-binding site.
