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CAS BI 385 Lecture Notes - B-Cell Receptor, Adaptive Immune System, Cytotoxic T Cell

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School
Boston University
Department
Biology
Course
CAS BI 385
Professor
Trevor Siggers

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Document Summary

Main difference from innate immunity- cell surface receptor: one type (b or t cell receptors, specific for one pathogen, receptor selection is selected and expanded. Structure of surface of immunoglobulin, ab, and t- cell receptor: ig- b cell receptor, soluble form= antibody, antigen binding site in light chain. Highly variable regions: ig domain- small modular protein domain used in many immune system receptors, tcr"s: do not have a soluble form, antigen binding site has highly variable regions. Antibodies specificity: specific to their target pathogen. Gene rearrangement is a mechanism for generating diversity: gene segments- v, j, d, rearrangements make functional proteins, only happen in b and t cells. Clonal selection- guiding principle of adaptive immunity: clonal selection- lymphocyte selection, clonal expansion- only a few lymphocytes will bind the pathogen. Class 1 present antigens from intracellular pathways. Occurs in all cells in the body*** Present antigens to cytotoxic t cells that defend against intracellular pathogens: viral or bacterial intracellular-peptides.

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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

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.

Please briefly explain reasoning for all questions.

1)

Which of the following is a component of a vertebrate kidney? (Select all correct choices.)
glomerulus
Bowman's capsule
renal tubules
collecting ducts
Malphigian tubules

2)

In organisms, the ability to control osmosis depends on the properties of the plasma membranes of individual cells. Based on their ability to permit the free movement of water and some solutes, these membranes are best described as: (select all correct choices)
impermeable.
permeable.
semipermeable.
diffusible.
impervious.

3)

True or false: The inner cell mass of the blastocyst becomes the embryo, while the outer cell layer of the blastocyst forms part of the placenta.
true
false

4)

Which of the following accurately characterizes the early cleavage divisions in most animals, although not necessarily in mammals?
They do not involve an increase in the size of the zygote.
They are directed by the zygote’s genome.
They are relatively slow.
They do not occur at the same time, so at any given moment the zygote may have an odd number of cells.
All of these choices are correct.

5)

A key difference between hormonal regulation of the reproductive systems of males and females is that:
LH and FSH are released only in females.
LH and FSH are released only in males.
LH and FSH are released cyclically in females but nearly continuously in males.
LH is released in males and FSH is released in females.
LH is released continuously in males and FSH is released cyclically in females.

6)

Compared to sexual reproduction, asexual reproduction: (select all correct choices)
requires less investment in attracting mates.
allows much more rapid population growth.
is rarely found as the sole mechanism of reproduction.
results in the production of genetically identical cells or individuals.
involves meiosis and fertilization as core processes.

7)

True or false: In response to LH and FSH, ovaries secrete estrogen and progesterone.
true
false

8)

During the luteal phase of the menstrual cycle, if the oocyte is not fertilized, a number of events occur which are listed below. Select the answer that places the events in the correct chronological order.

Events:
1. the lining of the uterus is shed
2. the corpus luteum secretes progesterone
3. follicle cells are converted to the corpus luteum
4. the corpus luteum degenerates
5. estrogen and progesterone levels fall

3, 2, 4, 5, 1

1, 2, 3, 4, 5

2, 4, 3, 1, 5

4, 3, 2, 1, 5
5, 2, 3, 4, 1

9)

If an antibody is missing its Fc fragment, what would happen if this antibody encounters its target antigen in the bloodstream? Select all correct choices.
The antibody would be able to bind the antigen at a specific epitope.
The antibody would be able to bind the antigen, but not at an epitope site.
The antibody would not be able to bind to the antigen.
The antibody would be able to activate components of the complement system.
The antibody would not be able to activate components of the complement system.

10)

If an individual carries a mutation that results in a complete lack of MHC class I proteins, how would the individual’s immune response be affected? Select all correct choices.
Memory cell antibodies would not be able to attach to antigen epitopes.
Cytotoxic T cells would not be able to target (and destroy) infected cells.
Helper T cells would not be able to interact with antigen-presenting cells.
Plasma cell antibodies would not be able to attach to antigen epitopes.

11)

If an individual carries a mutation that results in a complete lack of MHC class I proteins, how would the individual’s immune response be affected? Select all correct choices.
Memory cell antibodies would not be able to attach to antigen epitopes.
Cytotoxic T cells would not be able to target (and destroy) infected cells.
Helper T cells would not be able to interact with antigen-presenting cells.
Plasma cell antibodies would not be able to attach to antigen epitopes.

12)

Which of the following statements is true regarding T cell receptors? Select all correct choices.
They recognize antigen-MHC complexes.
They contain variable and constant regions.
They are composed of two heavy (H) chains and two light (L) chains.
They are formed by the rearrangement of V, J, C, and D gene segments.
They can be found in the bloodstream independent of T cells.