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IMM340H1 Lecture Notes - Lecture 4: Fc Receptor, Avidity, Epitope

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burgundymule401
26 Feb 2019
School
UTSG
Department
Immunology
Course
IMM340H1
Professor
Liliana Clemenza

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Document Summary

Fab has 1 antigen binding sight, fab2 has 2 antigen binding sights. This igg molecule has 3 constant domains, and theres an effector function of the antibody. Antibodies have 2 sites, theres the antigen binding sight and the effector site that binds to the pathogens, and the fc receptor binds to the effector domain. Antibodies can bind repetitive epitopes, or linear sequences or conformational eiptopes. The antigen and antibody have to bevery close to eachother to be able to react and complenetary is an issue. Affinity is defined as the strength of binding between one antigen binding site. Avidity is the sum of binding sites that hodl 2 molecules together. Avidity is higher than the affinity when one antibody is bound to 2 molecules at the same time because you have to consider 2 antigen binding sites. If we couple both the dnp and klh, we can make antibodies antibodies against both the klh and dnp.

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Related Questions

1. Neutralizing antibodies are effective at preventing
infection or toxicity mediated by pathogens or their toxic products. In fact, nearly all vaccines currently in use function by eliciting neutralizing antibodies. The most important feature of a neutralizing antibody is:
A. Having a high degree of multi-valency, such as being a pentamer or hexamer of immunoglobulin monomers
B. Having high affinity for the antigen
C. Being present at a high concentration in the circulation
D. Being efficient at activating the complement cascade
E. Having a long half-life in the body

2. IgM antibodies are much more efficient than IgG at activating the complement cascade. However, under certain circumstances, IgG antibodies will activate the complement pathway. One example of a situation in which IgG binding to its antigen will
NOT trigger the complement cascade is when:
A. The IgG antibodies bind to a multivalent soluble antigen in solution, such as a polysaccharide structure shed from a bacterial pathogen.
B. The IgG antibodies bind to a viral capsid protein that is present in more than 100 copies on the viral particle surface.
C. The IgG antibodies bind to a bacterial surface by recognizing a repetitive polysaccharide component of the bacterial capsule.
D. The IgG antibodies are binding self-antigens such as chromatin released from dead cells.
E. The IgG antibodies are neutralizing a bacterial toxin protein by blocking the receptor-attachment site on the toxin.

3. Antibody-dependent cell-mediated cytotoxicity (ADCC) is an important effector mechanism in immunity to virus infections. This immune pathway has also been exploited for clinical applications. For instance, patients with
various disorders, including rheumatoid arthritis and some B cell lymphomas, are treated with an antibody directed at CD20, a surface receptor expressed on all B cells. This antibody leads to the depletion of B cells from the patients by the actions of:
A. Natural killer (NK) cells
B. Cytotoxic CD8 T cells
C. Cytotoxic CD4 T cells
D. Activated macrophages
E. The complement cascade membrane attack complex

Question 1

The antigen specificity of a BCR...

A. depends on the isotype of that BCR.
B. is the same as the antigen specificity of the secreted form of antibody produced by that cell.
C. is different for each of the BCRs on a cell.
D. is different for each of the Fab regions of the BCR.

Question 2

All BCRs on the surface of a B cell in a lymph node...

A. will have the same type of light chain (kappa/lambda).
B. will have the same type of light chain with the same exact amino acid sequence.
C. will each have a different type of light chain.
D. will have a lambda light chain on one Fab and a kappa light chain on the other Fab.

Question 3

The isotype of an antibody is...

A. determined by the light chain.
B. another word for an immunoglobulin Fab region.
C. determined by the heavy chain constant region.
D. determined by the Fc portion.
E. None of the above are correct

Question 4

Characteristics of lgG are...

A. a molecular weight of 900,000 and 10 antigen binding sites in the secreted form.
B. 165,000 molecular weight in the monomeric form but it is usually secreted as dimer.
C. the presence of more heavy chain constant regions than most antibodies but the lowest concentration in blood.
D. 150,000 molecular weight and the highest concentrations of all antibodies in blood.
E. None of the above describe IgG.

Question 5

Characteristics of lgM are...

A. 900,000 molecular weight and the secreted form has 10 antigen binding sites.
B. 165,000 molecular weight in the monomeric form but it is usually secreted as dimer.
C .the presence of more heavy chain constant regions than most antibodies but the lowest concentration in blood.
D. 150,000 molecular weight and the highest concentrations of all antibodies in blood.
E. None of the above describe IgM.

True / False Questions

01. _____ Antibody is composed of 2identical long heavy chains and 2 identical shorter lightchains.

02. _____ Variable (V) and constant(C) regions are part of both heavy and light chains.

03. _____ Variable regions for heavyand light chains from the same antibody molecule are alwaysidentical.

04. _____ Variable region of lightchains are encoded by the DNA sequences that contain rearranged V,D, and J segments.

05. _____ Fc part of the antibody isnot important, F(ab’)2 fragment has the same binding andeffector capacity.

06. _____ Fab fragments are generatedby alternative splicing.

07. _____ J chain is used as asurrogate light chain during pre-B cell receptor testing forsuccessful V(D)J rearrangement.

08. _____ Binding of the antigen byantibody is stabilized by disulfide bonds.

09. _____ RAG1/2 are always expressedin B cells at high level, because B cells need RAG1/2 to constantlyrearrange their V regions.

10. _____ “N” (non template)nucleotides are added by TdT.

11. _____ The 12/23 rule is appliedduring class switching.

12. _____ For B cells, V(D)Jrecombination occurs only in the bone marrow.

13. _____ The process of somatichypermutation helps to improve specificity of the antibody.

14. _____ In late pro-B cells, Vsegment is rearranged with DJ segments.

15. _____ Failure to eliminateself-reactive B cells may lead to serious autoimmune diseases.

16. _____ Mature, naïve B cellsexpress IgD and any of the other classes of antibody (IgM, IgG,IgA, or IgE) on their surfaces.

17. _____ B1 cells are present in theperitoneal cavity, pleural spaces and brain.

18. _____ AID (activation inducedcytidine deaminase) is expressed only in B cells and it canintroduce breaks in double stranded DNA.

19. _____ Different classes (isotypes)of antibodies have different effector functions, which aretriggered by special receptors expressed by a variety of cells.

20. _____ Plasma cells are terminallydifferentiated cells that produce large quantities ofantibodies.

21. _____ Repeated exposure to thesame antigen eventually leads to immunological exhaustion and lackof immunity, because there is no room for new plasma cells in thebone marrow.

22. _____ Germinal centers arespecialized sites within the bone marrow where Ig genes ofactivated B cells undergo affinity maturation.

23. _____ B cells can present antigensto T helper cells.

24. _____ Co-stimulatory molecules arerequired for efficient generation of memory B cells.

25. _____ Lymphocytes migrate to thelymphoid tissues in response to chemokines.

26. _____ Class switching duringgerminal center reaction is a random process.

27. _____ T cell independent responsescan generate strong and long lasting B cell memory.

28. _____ Fc receptors that arepresent on many different cell types are crucial for removal of thepathogens.

29. _____ The ideal vaccine should bedesigned to mimic the natural course of infection without causingsymptoms of the disease.

30. _____ The protective immunity canbe generated against any pathogen because there is virtuallyunlimited number of possible V regions, thus any antigen can berecognize by an antibody.