Exam 4 Posted Answers

Exam 4 Posted Answers - BISC 307 Spring 2009 Exam 4 Answers...

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BISC 307 – Spring 2009 Exam 4 Answers 6 pts. 1. Write a 1, 2, or 3 in each blank to indicate whether these characteristics of acquired immunity apply to 1) antibody-mediated immunity, 2) cell-mediated immunity, or 3) both. ________ a. involved in rejection of transplanted tissue ANS: a-2, b-1, c-3, d-3, e-2, f-1 ________ b. requires binding of a lymphocyte to a free extracellular antigen ________ c. triggered by binding specific antigens to complementary lymphocyte receptors ________ d. involves formation of memory cells in response to initial exposure to antigen ________ e. primarily defends against virus-infected host cells ________ f. protects primarily against bacterial invaders 3 pts. 2. Which one of the following statements about class II MHC proteins is false? (c) a. They are found on the surface of B lymphocytes. b. They are found on the surfaces of dendritic cells. c. They are required for B-cells to bind foreign antigens. d. They are used by macrophages to present foreign antigens to helper T-cells. e. They are required for helper T-cells to stimulate the activity of cytotoxic T-cells. 4 pts. 3. Indicate whether each of the following statements is true or false by writing the word “True” or “False” in the blank. Do not write T or F. ANS: a-T, b-T, c-T, d-F ________ a. Activated helper T-cells stimulate cytotoxic T-cells by secretion of interleukin-2. ________ b. Plasma membranes of macrophages contain class I MHC proteins, class II MHC proteins, and CD28 proteins. ________ c. Macrophages secrete interleukin-1 to activate helper T-cells. ________ d. CD8-positive cells bind to antigens presented by class II MHC proteins. 4 pts. 4. Which of the following immune system defects would you expect to see in a strain of mutant mice with defective Fas receptors? Write as many numbers in the box as you think apply. Do not guess; points will be deducted for wrong answers. ANS: a, c, d, f a. abnormally high secretion of IgG b. low numbers of activated CD4-positive cells c. enlarged lymph nodes d. low production of sperm e. reduced secretion of IgM f. symptoms of autoimmune disease 4 pts. 5. If blood flow to the left lung is completely blocked by an embolism in the pulmonary artery, which one of the following would most likely occur? (d) a. Systemic arterial P O2 will be normal. b. Plasma pH will be higher than normal. c. Systemic arterial P CO2 will be lower than normal. d. P O2 in alveoli in the right lung will be approximately equal to P O2 in the inspired air. e. P O2 in alveoli in the right lung will be approximately equal to P O2 in the pulmonary vein. 1
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6 pts. 6. Trophoblast cells in the fetal part of the placenta come into close contact with maternal cells in the endometrium of the uterus. About 10 years ago, researchers in Virginia reported that these trophoblast cells express FAS ligand. What might be accomplished by this expression of FAS ligand, and why may this be necessary? ANS:
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Exam 4 Posted Answers - BISC 307 Spring 2009 Exam 4 Answers...

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