MCMP 422FINAL EXAM A

SPRING 2004

  1. (3 points) Several types of immune cells can directly destroy pathogens either by engulfing the pathogen (sometimes with the help of other molecules) or by directly causing the lysis (disruption of the membrane) of virally infected cells. Which of the following cells can directly destroy pathogens or pathogen infected cells?
  2. macrophages and neutrophils
  3. TH1 and TH2 T cells
  4. natural killer cells (NK)
  5. all of the above
  6. a and c
  1. (3 points) Which of the following are characteristics of INNATE immunity?
  2. present BEFORE a pathogen invades the body
  3. SPECIFIC for the invading pathogen and no other pathogen
  4. imparts LONG TERM immunity through memory cells
  5. none of the above
  6. b and c
  1. (3 points) Starbright is infected with strain A influenza virus on January 1. She comes down with a case of the flu, but is beginning to recover by January 15. On February 1, Starbright visits a sick friend and is exposed to both strain A influenza and Streptococcus pyogenes, the causative agent of strep throat. Starbright, believe it or not, has never had strep throat. On February 4th, Starbright’s blood is drawn and examined for antibodies to strain A influenza and antibodies to Streptococcus pyogenes. Which of the following is/are MOST LIKELY to be found in Starbright’s blood on February 4th?
  2. a low antibody titer (few antibodies) for strain A influenza
  3. a high antibody titer for strain A influenza AND a high antibody titer for Streptococcus pyogenes
  4. a high antibody titer for strain A influenza AND a low antibody titer for Streptococcus pyogenes
  5. a low antibody titer for strain A influenza AND a low antibody titer for Streptococcus pyogenes
  6. a low antibody titer for strain A influenza AND a high antibody titer for Streptococcus pyogenes
  1. (3 points) There are several types of recognition molecules in the immune system that recognize (bind to) “antigens”. Which of the following is TRUE regarding recognition molecules in the immune system?
  2. The B cell antigen receptor (BCR) and the T cell antigen receptor (TCR) both recognize short peptide sequences (8-10 amino acids or 13 to 25 amino acids) derived from pathogenic proteins
  3. Both the TCR and MHC molecules recognize short peptide sequences (8-10 amino acids or 13 to 25 amino acids) derived from pathogenic proteins
  4. The BCR and the TCR both recognize intact protein antigens (i.e., protein antigens that have NOT been proteolyzed (degraded))
  5. Both the BCR and MHC molecules recognize short peptide sequences (8-10 amino acids or 13 to 25 amino acids) derived from pathogenic proteins
  6. The antigen receptors on natural killer cells recognize both intact antigen and short antigen derived peptide sequences

5. (3 points) The clonal selection theory lies at the heart of the immune response. Which of the following BEST describes the clonal selection theory?

a. Before puberty millions of lymphocytes are generated each day in the human. Each INDIVIDUAL lymphocyte expresses thousands of IDENTICAL receptors for a specific antigenic determinant (epitope). After a pathogen enters the body, a lymphocyte with receptors that recognize a specific antigenic determinant within the pathogen is stimulated to divide. This generates a clone of lymphocytes that recognize a specific epitope within the pathogen.

b. Before puberty millions of lymphocytes are generated each day in the human. Each INDIVIDUAL lymphocyte expresses thousands of DIFFERENT receptors that recognize different antigenic determinants within the pathogen. After a pathogen enters the body, a lymphocyte that expresses several receptors that recognize several different epitopes within the pathogen is stimulated to divide. This generates a clone of lymphocytes that recognize several different epitopes within the pathogen.

c. Lymphocytes that express receptors for specific antigenic determinants are generated only AFTER a pathogen enters the body.

d. Lymphocytes do not express receptors that are specific for antigenic determinants within pathogens.

e. none of the above answers provides a good description of the clonal selection theory.

6. (3 points) Which of the following is/are NOT a function of the Fc regions of immunoglobulin (antibody) molecules?

a. opsonization of bacteria

b. neutralizing toxins

c. serving as the BCR on B cells and in this capacity binding intact pathogens

d. all of the above are NOT functions of the Fc regions of immunoglobulins

e. b and c

7. (3 points) Which of the following cells can function at the site of an infection WITHOUT having to be first activated at a distal (far away) site?

a. CD8+ T cells

b. TH2 T cells

c. macrophages and neutrophils

d. B cells

e. a and b

8. (3 points) Immunoglobulins (antibodies (Abs)) specifically bind to antigenic determinants on the surface of pathogens. Which of the following is/are TRUE regarding the physical interaction between an immunoglobulin molecule and an antigenic determinant?

a. The interaction involves the antigenic determinant and a region of the Ab that contains roughly the first 100 amino acids of the light and heavy chains.

b. All the amino acid residues in the light chain of the Ab molecule that physically contact the antigenic determinant are found next to each other in the LINEAR sequence of the light chain.

c. All the amino acid residues in the heavy chain of the Ab molecule that physically contact the antigenic determinant are found next to each other in the LINEAR sequence of the heavy chain.

d. all of the above

e. a and b

9. (3 points) When the sequence of the DNA encoding the BCRs and TCRs is determined in a hematopoietic stem cell, the DNA encoding the variable regions and the constant regions of the receptors are located far apart on the chromosome. When the same sequence is determined in a mature lymphocyte, the DNA encoding the variable region and the constant region of the expressed antigen receptor are adjacent (next to each other) on the chromosome. Which of the following statements is/are TRUE regarding this observation?

a. This rearrangement of DNA evolved as a mechanism to generate diversity in the immune system

b. This rearrangement of DNA occurs AFTER a pathogen enters the body and is directed by the specific antigenic determinants on the pathogen

c. This rearrangement of DNA is not directed by a pathogen, but occurs randomly, in the absence of a pathogen

d. This rearrangement of DNA occurs in the secondary lymphoid tissues

e. a and c

10. (3 points) Although the regions of antigen receptors on the protein level are generally referred to as variable (V) and constant (C), on the DNA level they actually include other regions. Regarding these other regions, which of the following statements is/are TRUE regarding this observation?

  1. Both the DNA encoding the constant regions of the BCR light chains and the constant regions of the TCR alpha () chains contain J segments
  2. Both the DNA encoding the constant regions of the BCR heavy chains and the constant regions of the TCR beta () chains contain J segments and D segments
  3. The J segments of the antigen receptor DNA are located between the first and second domain of the constant region in both the BCR and the TCR
  4. a and b
  5. none of the above

11. (3 points) Unlike TCRs, BCRs continue to evolve during an immune response. Which of the following is/are TRUE regarding the evolution of BCRs?

a. B cells expressing BCRs of higher affinity for a particular pathogen are selected for survival in the germinal centers of lymph nodes BEFORE the pathogen enters the body

b. B cells expressing BCRs of higher affinity for a particular pathogen are selected for survival in the germinal centers of lymph nodes AFTER the pathogen enters the body

c. BCRs of higher affinity for a pathogen are generated by random point (single amino acid) mutations in the variable regions of both the light and heavy chains

d. none of the above

e. b and c

12 (3 points) Antigen presentation by MHC molecules is critical to an effective immune response. Which of the following is/are TRUE regarding the presentation of antigen by MHC molecules?

a. MHC I molecules present “antigen” to cytotoxic (killer) T cells

b. MHC class II molecules present “antigen” to TH1 and TH2 cells T cells

c. MHC I molecules are mainly responsible for presenting viral “ antigens” to the

appropriate lymphocytes

d. all of the above

e. a and b

13 (3 points) Where a pathogen replicates in the body dictates how it will be “seen” by the immune system. Which of the following is/are TRUE regarding how the immune system reacts to pathogens?

  1. Peptides from bacteria replicating outside of cells are presented to T cells by MCH class II molecules
  2. Peptides from viruses are presented to T cells by MHC class I molecules
  3. Peptides from viruses are degraded in the cytosol by proteasomes and transported into the endoplasmic reticulum, while peptides from extracellular bacteria are degraded in the phagolysosome
  4. all of the above
  5. none of the above

14. (3 points) Which of the following is/are TRUE regarding MHC molecules and the DNA that encodes them?

  1. The MHC locus (DNA that encodes MHC molecules) is said to be the most polymorphic locus in the human genome. This means that the DNA at this locus undergoes frequent recombination to generate several different versions of both MHC I and MHC II molecules
  2. A single cell can express both MHC I and MHC II molecules, but on that single cell all the MHC I molecules will be identical and all the MHC II molecules will be identical
  3. In the absence of foreign antigens MHC I and MHC II molecules are synthesized, but remain in the cell and are not transported to the cell surface
  4. none of the above
  5. a and b

15. (3 points) The following is found on a hospital chart for patient X: HLA-A12A35 HLA-B115B200 HLA-C52C19. What do these letter and numbers describe?

  1. The composition of the patient’s T cell repertoire
  2. The composition of the patient’s B cell repertoire
  3. The patient’s inherited haplotypes for MHC class I
  4. none of the above
  5. a and b

16. (3 points) Approximately 30 billion B cells are produced and leave the bone marrow each day. Which of the following is/are TRUE regarding B cell development in the bone marrow?

  1. B cells mature in the bone marrow (i.e. differentiate from pro- B cells to mature B cells) in the ABSENCE of DNA rearrangement
  2. B cells maturing in the bone marrow need to rearrange the DNA for EITHER the heavy chain of the BCR or the light chain of the BCR, but NOT both.
  3. During B cell development, the heavy chain DNA must move a D region segment next to a J region segment and move the DJ combined segment next to a V region segment before the DNA for the light chain can rearrange
  4. Regardless of whether the DNA rearrangement on the initial chromosome is productive or not, the DNA on the second chromosome will NEVER rearrange
  5. none of the above

17. (3 points) During B cell development in the bone morrow most of the developing B cells will die. Which of the following is/are TRUE regarding B cell death in the bone marrow?

  1. B cells that FAIL to rearrange their heavy chain DNA on BOTH copies of the chromosome will die by apoptosis
  2. During B cell development, B cells that have rearranged their heavy chain, but NOT their light chain are signaled to die if they encounter a self antigen
  3. During B cell development, B cells that have rearranged their heavy chain, AND their light chain are signaled to die if they encounter a self antigen
  4. Developing B cells can not leave the bone marrow until the have successfully rearranged BOTH the  and  chains of the T cell antigen receptor (TCR)
  5. a and c

18. (3 points) Which of the following is/are TRUE regarding germinal centers in the secondary lymphoid tissues?

  1. They form during an immune response and contain among other cells, centroblasts, centrocytes and follicular dendritic cells (FDCs)
  2. Somatic hypermutation and affinity maturation occur in germinal centers
  3. The switch from IgM synthesis to IgG or IgA or IgE synthesis occurs in the germinal centers
  4. all of the above
  5. b and c

19 (3 points) As T cells develop in the thymus they go through several stages of maturation and migrate from the cortex to the medulla. Which of the following is/are TRUE regarding T cell development?

  1. T cells MUST rearrange their DNA for the  and  (or  and ) chains of the TCR if they are to develop into mature T cells
  2. During NEGATIVE selection, strong engagement of the TCR is a signal to SURVIVE
  3. During POSITIVE selection, T cells that recognize self MHC are signaled to DIE by apoptosis
  4. all of the above
  5. none of the above

20 (3 points) A mouse of strain X undergoes whole body irradiation that destroys all bone marrow cells, but all other cells and tissues remain healthy. The irradiated mouse is given a bone marrow transplant from an UNRELATED strain Y mouse that shares NO MHC alleles with strain X. Which of the following will occur in the transplanted strain X animal?

  1. T cells that arise from the strain Y mouse (strain Y T cells) will not develop in the thymus of the irradiated strain X mouse because they will not recognize self MHC molecules
  2. Strain Y T cells will develop in the irradiated strain X mouse and those passing positive selection will recognize strain X MHC as self
  3. Macrophages that develop in the irradiated strain X mouse will express strain X MHC molecules
  4. None of the above
  5. a and c

21. (3 points) Which of the follow is/are TRUE regarding either the expression or the function of CD4 and CD8?

  1. T cells undergoing positive selection in the thymus will express both CD4 and CD8 on their surface (double positive T cells)
  2. Both CD4 and CD8 bind MHC molecules, but the class of MHC molecule they bind is different
  3. Only T cells that express either CD4 or CD8, but not BOTH will leave the thymus
  4. All of the above
  5. a and b

22. (3 points) Mature, naive T cells that leave the thymus

  1. circulate in the blood and lymph and congregate in the T cells enriched areas of lymph nodes, spleen and mucosal tissue
  2. encounter foreign peptides for the first time at the site of an infection
  3. can survive for long periods of time in the absence of antigenic stimulation
  4. all of the above
  5. a and c

23. (3 points) Which of the following are professional antigen presenting cells (APCs).

  1. dendritic cells
  2. B cells
  3. macrophages
  4. all of the above
  5. b and c

24. (3 points) The secondary lymphoid tissues are important places for immune function. Which of the following is/are TRUE regarding secondary lymphoid tissues?

  1. pathogens arrive in the lymph nodes by: 1) the lymph and 2) dendritic cells that ingest the pathogen at the site of an infection and migrate to the lymph nodes
  2. macrophages in the T cell area of the lymph nodes ingest pathogens that arrive by the lymph and along with dendritic cells present foreign antigens to passing naïve T cells
  3. all the CD8+ T cells, but only a subset of the CD4+ T cells leave the lymph nodes once they have encounted foreign peptide for the first time
  4. all of the above
  5. a and b

25. (3 points) “Co-stimulation” of T-cells is essential for the effective function of the immune system. Which of the following is/are TRUE regarding co-stimulation?

  1. developing T cells in the thymus require co-stimulation to progress from positive selection to negative selection
  2. developing T cells in the thymus require co-stimulation to progress from double positive cells to single positive cells
  3. naïve T cells that bind antigen in the ABSENCE of co-stimulation become anergic
  4. all of the above
  5. a and c

26. (3 points) Naïve T cells stimulated by MHC molecules presenting foreign peptides on cells that DO NOT also express B7 will

  1. fail to synthesize and express BOTH interleukin 2 (IL-2) and the high affinity receptor for IL-2 (IL-2R)
  2. secrete cytokines that mediate inflammation
  3. secrete cytokines that help B cells differentiate
  4. none of the above
  5. b and c

27. (3 points) Cyclosporin A and tacrolimus (FK506) are used in patients receiving transplants to suppress the immune system. These drugs PRIMARILY inhibit

  1. B cell development in the bone marrow
  2. T cell growth (clonal expansion) in the periphery (circulation)
  3. marcophage function
  4. dendritic cell function
  5. mast cell degranulation

28. (3 points) The balance between different T cell subsets is critical to the outcome of an immune response. Patients infected with Mycobacterium leprae for example can have radically different outcomes depending on which set of T cells dominant the immune response. Which of the following is/are TRUE regarding Mycobacterium lepra.

  1. Mycobacterium leprae is a bacterium that grows within the vesicular system of macrophages and therefore escapes the immune system
  2. If the immune system responds to Mycobacterium leprae by primarily producing IFN-, TNF-, TNF- and IL-3 the patient’s macrophages will be activated to kill the intracellular Mycobacterium leprae and the patient will likely survive
  3. If the immune system responds to Mycobacterium leprae by primarily producing IL-4 and IL-5, the patient’s B cells will be activated resulting in antibody production, but these antibodies will be largely ineffective against the intracellular Mycobacterium leprae and the patient will likely die
  4. all of the above
  5. a and c

29. (3 points) Effector T cells are T cells that previously have been primed (seen antigen before). Which of the following is/are TRUE regarding effector T cells?

  1. the next time an effector CD8+ cell sees foreign peptides properly presented, it will kill the cells presenting those peptides
  2. the next time an effector TH1 cell sees foreign peptides properly presented, it will secrete inflammatory cytokines resulting in macrophage activation
  3. effector T cells to not need co-stimulation to react to foreign peptide antigens when properly presented
  4. all of the above
  5. a and b

30. (3 points) Individuals who know they are allergic to rag weed or pollen will respond in seconds to the presence of the allergen. This quick response time results from

  1. the fact that IgE is the most quickly synthesized Ab in the body and can be produced and secreted almost instantaneously
  2. the fact that mast cells and basophils have high affinity receptors for IgE so that they continually have IgE on their surface
  3. the fact that parasites are usually present within the body where they continuously stimulate the production of IgE
  4. the fact that the DNA for IgE does NOT have to be rearranged
  5. the fact that IgE is the only immunoglobulin that does not require the presence of a light chain to bind antigen

31. (3 points) Which of the following are greatly aided in “doing their job” by the presence of IgG molecules that are specific for a pathogen?