Questions for Which More Than One Answer Was Accepted Are Highlighted in Red
MCMP 422FINAL EXAM BLUE
SPRING 2005
Questions for which more than one answer was accepted are highlighted in red.
1. (2 points) One manifestation of ACADEMIC DISHONESTY is cheating on exams. In the beginning of the semester the policy on ACADEMIC DISHONESTY for MCMP 422 was distributed to you and read to you by Dr. Harrison. ACADEMIC DISHONESTY includes, but is not limited to: copying from another exam during the examination period; and/or allowing your exam/scantron to be seen by a classmate during the examination period. The policy for ACADEMIC DISHONESTY in MCMP 422 is an automatic F grade for the ENTIRE course.
a. True
b. True
Please keep this in mind as you continue with this exam.
2. (3 points) The immune system encompasses amazing physiological processes that have evolved to protect us from almost all pathogens. Which of the following is/are critical (very important) components (parts) of the immune system?
a. the heart
b. the pancreas
c. the bone marrow
d. a and b
e. none of the above
3. (3 points) In 1796 Edward Jenner, an English doctor, inoculated a boy with pus from a cowpox (very similar to smallpox) lesion (sore). Several weeks later, Dr. Jenner purposely exposed the boy to deadly smallpox. The boy played happily following his encounter with smallpox and never developed the disease. What had doctor Jenner proved?
a. the body has an innate immune system
b. the body has an adaptive immune system
c. the body has a complement system
d. a and c
e. none of the above
4. (3 points) The complement system is very important in protecting us against dangerous microbes. Individuals with genetic (inherited) defects in the complement system suffer from various syndromes (bad conditions) ranging from autoimmunity (counter-intuitive) to susceptibility to disease (intuitive). (Intuitive means it makes sense, counter-intuitive means it makes no sense). Which of the following most likely explains the fact that some individuals with defects in their complement system are susceptible to an autoimmune disease? Note: the correct answer to this question is not known. I want you to decide which of the choices makes the most sense based on your knowledge of immunology.
a. defects in complement would lead to a MORE rapid clearing of bacteria from the body and this could lead to the immune system attacking itself since there are no pathogens to attack
b. a major function of complement is to regulate acquired immunity by suppressing lymphocyte activation; a defect in complement would lead to unregulated lymphocyte activation resulting in autoimmunity
c. one function of complement is to rid the body of immune complexes by covalently attaching to the antibodies in these complexes. Red blood cells have receptors for complement and transport the immune complexes to the spleen and liver for removal by phagocytic cells; failure to remove immune complexes can lead to autoimmunity
d. a and b
e. all of the above are equally likely based on the current knowledge of how complement functions
5. (3 points) Immunology is a YOUNG science only emerging in the mid-1900’s (This is VERY young as Dr. Harrison was born in 1948!!). During her formative years, in the 1950s, a debate raged among immunologists as to how cells in the body were triggered to make antibodies to different antigens. Which of the following theories proposed at the time turned out to be correct?
a. a single cell that will make antibodies has receptors for many different antigens on its surface. When an antigen binds the receptor that “recognizes” it, the cell is stimulated to make only that receptor and not the other receptors that are present on its surface.
b. each cell that will make antibodies has receptors for antigen on its surface that are identical, but the receptors differ from cell to cell. Antigens will bind to the cell whose receptors “recognize” it and stimulate that cell to make the receptors that are on its surface.
c. antibodies are not related to the receptors for antigen on the surface of the cells that will eventually make the antibodies. An antigen enters B lymphocytes by phagocytosis, travels to the nucleus and “turns on” the specific gene that encodes the antibody that will recognize it.
d. antibodies are stored in plasma cells BEFORE an antigen enters the body. Immediately (seconds)after an antigen binds to a plasma cell that has surface receptors for that antigen, the plasma cell will “degranulate” and secrete the antibodies it has stored inside.
e. none of the above turned out to be correct
6. (3 points) During B lymphocyte development, a variable region (V) DNA segment is moved next to a joining (J) region DNA segment. In case 1, the eleventh variable region (V11) DNA segment is moved next to the first joining region (J1) DNA segment to create a V11J1 DNA segment that is linked to the constant region of the kappa () chain DNA. In case 2, the ninth variable region (V9) DNA segment is moved next to the fifth joining region (J5) DNA segment to create a V9J5 DNA segment that is linked to the constant region of the kappa () chain DNA. Both V11J1 and V9J5 code for functional proteins. Which of the following is/are true?
a. case 1 and case 2 occur in the same developing B cell
b.V11J1 and V9J5 will have the same CDR2 region
c.V11J1 and V9J5 will have the same CDR3 region
d.V11J1 and V9J5 will be bound to each other by disulfide bonds to form the antigen binding region of the BCR
e.none of the above
7. (3 points) What is the function of effector CD8+ T cells?
a. to kill cells they bind to
b. to present antigen to TH1 cells
c. to present antigen to TH2 cells
d. b and c
e. none of the above
8. (3 points) Diversity is essential for survival in all species and this is dramatically illustrated in vertebrates by the immune system. How does the human immune system achieve its remarkable diversity? (READ THIS QUESTION CAREFULLY)
a. some (not all) elements of diversity are inherited and the MHC system is a good example. The extensive polymorphism in the human MHC makes it unlikely that the entire human race will be extinguished by a single pathogen.
b. some (not all) elements of diversity are generated by random recombination of DNA (somatic recombination). The antigen receptors on T and B lymphocytes are a good example of the random generation of key immune molecules.
c. some (not all) elements of diversity are inherited AND generated by random recombination of DNA. CD4 is a good example of this where the different forms of CD4 in individuals can result from both differential inheritance and random recombination of segments of the CD4 genes in T lymphocytes.
d. a and b
e. all of the above
9. (3 points) The five major classes of immunoglobulins (Ig, antibodies) share a basic structure, although they may differ in the number of heavy chain domains and the number of “Ig units” in a molecule. Which of the following is/are TRUE regarding Ig (antibody) molecules?
a. variable regions are present only in the heavy chains
b. variable regions are present only in the light chains
c. the complementarity determining regions (CDRs) are located in the constant region of the light chains
d. The Fc regions of IgM and IgD are the same, although they are different from the Fc regions of IgG, IgA and IgE.
e. none of the above
10. (3 points) The receptors on the surface of T lymphocytes and B lymphocytes are responsible for the exquisite specificity of the immune response. Which of the following is/are TRUE regarding BCRs and TCRs?
a. BCRs bind epitopes on “intact” antigens (e.g., proteins on the surface of bacteria) and these same epitopes will be the target of any antibodies that mightresult.
b. BCRs do not bind epitopes on intact antigens, but rather bind small peptides generated from antigens.
c. While TCRs can only bind epitopes that are on the external surface of the intact antigen, BCRs can bind peptides whose amino acids are buried within the three dimensional structure of the intact antigen.
d. a and b
e. all of the above
11. (3 points) The different fates of individuals infected with Mycobacterium leprae illustrate the consequences when the immune response becomes biased toward either a TH1 or a TH2 response. Which of the following is/are TRUE regarding TH1 and TH2 cells?
a. Effector TH1 cells are cytotoxic (killer T cells) while effector TH2 cells are “helper” cells (i.e., they “help” B cells make antibodies).
b. Both effector TH1 cells and effector TH2 cells recognize antibody bound to MHC II.
c. Effector TH1 cells must travel to the site of an infection to function, while effector TH2 cells function in the secondary lymphoid tissues where they were activated.
d. b and c
e. all of the above
12. (3 points) What happens on the surface of a dendritic cell when there are NO pathogenic proteins to be processed and presented?
a. There will be NO MHC molecules on the surface of the dendritic cell
b. Only MHC II molecules containing bound CLIP will be present on the surface of the dendritic cell
c. Only “empty” MHC I molecules (MHC I molecules NOT containing bound peptide) will be present on the surface of the dendritic cell
d. Both MHC I and MCH II molecules will be present on the surface of the dendritic cell, but neither will contain bound peptides.
e. none of the above
13. (3 points) Which of the following is/are TRUE regarding MHC molecules and how they function?
a. all nucleated (have a nucleus) cells express MHC molecules on their surface. On a single liver cell, all the MHC molecules are identical.
b. some cells can express both MHC I and MHC II simultaneously. On those cells all the MHC I molecules will be identical and all the MHC II molecules will be identical, but the MHC I molecules will be different from the MHC II molecules
c. cells that express MHC I can be effectively killed by the appropriate immune cell if the MHC I expressing cell becomes virally infected.
d. b and c
e. all of the above
14. (3 points) During B cell development, V, D, and J regions are randomly rearranged and joined. Which of the following is/are TRUE regarding these rearrangement events?
a. the rearrangement occurs in the DNA, such that deoxynucleotides are rearranged and joined together
b. the rearrangement occurs in the RNA, such that ribonucleotides are rearranged and joined together
c. the rearrangement occurs in the protein, such that amino acids are rearranged and joined.
d. the rearrangement and joining occurs BEFORE isotype switching
e. a and d
15. (3 points) During B cell development a stem cell is differentiated through several stages into a mature B cell. Which of the following statements is/are TRUE regarding this process?
a. it occurs in the bone marrow in the ABSENCE of antigen
b. it involves the sequential rearrangement of DNA that results in genes that will encode the chains of the BCR
c. self-reactive B cells are eliminated at the large pre-B cell stage where the cell expresses on its surface a pre-B cell receptor consisting of a rearranged heavy chain and a surrogate light chain
d. a and b
e. all of the above
16. (3 points) Although many billions of B cells begin to develop each day, only a very few survive to become plasma cells. Which of the following statements is/are TRUE regarding the survival of B cells?
a. many developing B cells die by apoptosis during development because they fail to productively rearrange their DNA
b. B cells that mature and enter the circulation need survival signals or they will die. Follicular dendritic cells (FDCs) can provide those needed survival signals, but there are too many B cells and not enough FDCs, so most mature B cells die.
c. mature B cells that enter the circulation need the “help” of CD8+ T cells to survive. Most circulating B cells will fail to encounter a CD8+ T cell resulting in massive B cell death.
d. a and b
e. none of the above
17. (3 points) Which of the following is/are TRUE regarding the function of B cells in the immune system?
a. mature, naïve, circulating B cells have both IgM and IgD on their surface
b. naïve B cellsmeettheir antigen for the first time in the T cell area of the secondary lymphoid tissue
c. an antigen bound B cell presents antigen to T cells in the secondary lymphoid tissue. A CD4+ T cell that recognizes antigen presented by a B cell will bind to that B cell and the pair will move into a secondary lymphoid follicle where the B cell becomes a rapidly dividing centroblast that can undergo both somatic hypermutation and isotype switching.
d. all of the above
e. a and b
18. (3 points) During an immune response the antibodies that are generated become more effective over time. Which of the following statements is/are TRUE regarding the increasing strength of the immune response during prolonged exposure to a pathogen?
a. after an initial encounter with a pathogen, some B cells will immediately differentiate in the secondary lymphoid tissue into plasma cells that secrete low affinity IgM
b. after an initial encounter with a pathogen, B cells receiving T cell “help” will migrate and form germinal centers where point mutations in the variable regions of the genes that encode the heavy and light chains occur.
c. B cells that have undergone somatic hypermutation are selected for those B cell that have high affinity receptors by antigen that is bound on the surface of follicular dendritic cells
d. b and c
e. all of the above
19. (3 points) T cells are absolutely required for an effective immune response against pathogens that are not eliminated by the innate immune system. Which of the following statements is/are TRUE regarding T cells?
a. the antigen binding portion of the TCR is composed of the variable regions of an and chain
b. the antigen binding portion of the TCR binds ONLY the antigenic peptide and does not bind the MHC molecule presenting the peptide
c. the DNA encoding different TCRs is inherited and unlike BCRs is NOT generated by random DNA rearrangement.
d. a and b
e. none of the above
20. (3 points) T cells undergo a development process starting with a double negative T cell progenitor and ending with a mature, circulating naïve T cell. Which of the following is/are TRUE regarding the development of T cells?
a. double negative T cells enter the thymus and start to rearrange their CD4 genes first
b. double negative T cells enter the thymus and start to rearrange their CD8 genes first
c. developing T cells undergo positive selection AFTER the chain has rearranged, but BEFORE the chain has rearranged
d, a and c
e. none of the above
21. (3 points) The central and powerful role that T cells play in the immune system necessitates that their development be highly regulated, which involves both the processes of positive and negative regulation. Which of the following is/are TRUE regarding the regulation of T cell development?
a. once “gene rearrangement” is completed, developing double positive T cells undergo positive selection. They pass POSITIVE selection only if their TCRs can recognize (bind) self MHC molecules that are present on the surface of thymic cortical epithelial cells.
b. T cells undergoing NEGATIVE selection will automatically die unless they bind self MHC presenting self peptides tightly enough to receive a signal to survive
c. positive selection occurs before negative selection
d. a and c
e. all of the above
22. (3 points) The immune system contains many different cells that perform various functions all with the goal of eliminating pathogens. Which of the following statements is/are TRUE?
a. neutrophils are phagocytic cells that circulate in the blood until they encounter chemokines (secreted by immune cells at the site of an infection) that direct their migration out of the blood and into the infected area.
b. mature naïve B cells are long lived, where as mature naïve T cells usually don’t survive longer than a few weeks.
c. macrophages reside in tissues and are one of the first immune cells to encounter pathogens
d. a and c
e. all of the above
23. ( points) Once T cells develop and obtain the capacity to react with antigen, they circulate in the blood awaiting their BIG MOMENT. Which of the following statements is/are TRUE regarding the activation of T cells?
a. the first encounter with an antigen is called “priming” or activation because it readies the T cell for the second encounter, which results in the T cell either killing the cell presenting antigen to it (CD8+ cells) OR in secreting cytokines (CD4+ cells).
b. if a B cell presents peptide X to an effector T cell, that T cell could have been activated by a macrophage as long as the macrophage presented peptide X
c. naïve T cells circulate in the blood until they encounter chemokines (secreted by macrophages at the site of an infection) that direct their migration out of the blood and into the infected area.
d. a and b
e. none of the above
24. (3 points) T cells that circulate in the blood enter the lymph nodes. How do they know when they have reached a lymph node?
a. they are carried to the lymph nodes by binding to dendritic cells that enter the lymphatics