1. How do killer T cells eliminate virus-infected cells?

A. By producing antibodies specific to the virus B. By triggering the infected cell to commit suicide C. By engulfing the virus directly D. By neutralizing the virus before it infects cells

2. What is the role of regulatory T cells in the immune system?

A. To increase antibody production during infections B. To enhance inflammatory responses against pathogens C. To prevent the immune system from overreacting and causing autoimmunity D. To directly kill infected cells via cytotoxicity

3. What principle do both B cells and T cells obey during antigen response?

A. Phagocytosis B. Clonal selection C. Direct neutralization D. Innate recognition

4. What process enables macrophages to destroy bacteria after engulfing them?

A. Antibody production B. Phagocytosis followed by fusion with lysosomes C. Release of antibodies D. Direct killing by cytotoxic molecules

5. What does the innate immune system provide to the adaptive immune system?

A. Antigen-specific receptors B. Non-specific defense only C. Evaluation of danger and instruction to mount specific responses D. Memory cells

6. Why are memory B and T cells easier to activate than naive cells?

A. They are more abundant and have undergone prior activation B. They do not require antigen recognition C. They do not require the second signal for activation D. They are continuously producing antibodies

7. How does the immune system prevent attacking self molecules?

A. By producing antibodies against self-antigens B. Through education processes that induce tolerance in B and T cells C. By eliminating all B and T cells before maturation D. Using only innate immunity

8. What is the role of antigen-presenting cells (APCs) in adaptive immunity?

A. To secrete antibodies B. To display antigen fragments to T cells using MHC molecules C. To kill infected cells D. To produce cytokines that directly kill bacteria

9. How do class I MHC molecules contribute to immune defense?

A. By displaying fragments of extracellular bacteria to helper T cells B. By presenting viral peptides on infected cells to killer T cells for surveillance C. By activating B cells to produce antibodies D. By producing cytokines that recruit other immune cells

10. What is the main function of memory B and T cells in the adaptive immune system?

A. To continuously produce antibodies regardless of infection B. To survive long-term and enable a faster response upon re-exposure to the same antigen C. To destroy infected cells during the first infection only D. To present antigens to macrophages during infections

11. What kind of proteins are antibodies?

A. Lipids B. Carbohydrates C. Special proteins circulating in blood that recognize antigens D. Enzymes that digest pathogens

12. Why do B and T cells require a "two-key system" for activation in the adaptive immune response?

A. Because they need to recognize two different pathogens simultaneously. B. To ensure they are only activated at the appropriate time and place to prevent unintended damage. C. To allow them to function without the help of antigen-presenting cells. D. Because the first key activates killer T cells and the second activates helper T cells.

13. Why is immunological memory beneficial to the immune system?

A. It allows antibodies to continuously circulate without any infection B. It ensures a faster and stronger immune response upon subsequent exposure to the same pathogen C. It prevents the activation of the innate immune system D. It causes the immune system to always attack self-molecules indiscriminately

14. Which type of MHC molecule is expressed on almost all nucleated cells?

A. Class I MHC B. Class II MHC C. Class III MHC D. None of the above

15. Which cells are the first to respond to invading microbes breaching the physical barrier?

A. B cells B. T cells C. Macrophages D. Antibodies

16. What specific process allows macrophages to digest bacteria?

A. Phagocytosis followed by enzymatic degradation in lysosomes B. Secretion of antibodies C. Direct lysis of bacterial DNA D. Production of cytokines only

17. What makes T cell receptors (TCRs) diverse?

A. Multiple gene rearrangements producing a modular design B. Fixed gene sequence common to all cells C. Only a single gene controls TCR diversity D. They are identical to B cell antibodies

18. What is the primary role of antibodies in the immune system?

A. To directly kill invading pathogens B. To produce cytokines that fight infection C. To tag invaders for destruction by other immune cells D. To destroy infected human cells

19. What is immunological memory?

A. The production of antibodies immediately after infection B. The ability of the immune system to remember and respond faster to a previously encountered antigen C. The death of immune cells after infection D. The activation of innate immunity

20. In the context of the adaptive immune system, what does “clonal selection” refer to?

A. The selection of macrophages that will engulf pathogens B. The proliferation of B or T cells that recognize a specific antigen after activation C. The process of antibody production by plasma cells D. The elimination of autoreactive immune cells in the thymus

21. How does the adaptive immune system recognize dangerous from harmless molecules?

A. By directly detecting pathogens’ molecular structures B. By relying on the innate immune system to signal danger C. Through antibody diversity alone D. By using receptors that recognize all self molecules

22. Why is the innate immune system described as "already in place"?

A. It is always ready to respond rapidly to many common pathogens B. It requires prior exposure to function C. It produces antibodies which take days to develop D. It only acts after adaptive immunity is activated

23. Which antibody class is associated with hypersensitivity and allergic reactions?

A. IgG B. IgA C. IgE D. IgM

24. Which type of adaptive immune cell requires antigen presentation by Class I MHC molecules for activation?

A. Helper T cells B. Killer (cytotoxic) T cells C. B cells D. Macrophages

25. What is the function of regulatory T cells in immune response?

A. Assist B cells in producing antibodies B. Kill infected cells directly C. Help keep the immune system from overreacting D. Present antigens to other cells

26. What happens to most activated B and T cells after an infection is cleared?

A. They become antigen-presenting cells B. They all remain active indefinitely C. Most undergo apoptosis, leaving memory cells behind D. They convert into macrophages

27. What is the main function of the Fc region of an antibody?

A. Bind directly to antigen B. Bind to Fc receptors on immune cells and determine antibody class C. Neutralize viruses by itself D. Destroy cells infected by viruses

28. What major problem does the diversity of B cell receptors and T cell receptors create?

A. Inability to recognize pathogens B. High risk of attacking self molecules C. Slow immune response D. Excessive antibody production

29. What molecules act as "billboards" to present antigen fragments to T cells?

A. Cytokines B. Toll-like receptors C. Major Histocompatibility Complex (MHC) molecules D. Antibodies

30. Which of the following best describes the role of the innate immune system in relation to the adaptive immune system?

A. It produces antibodies that directly kill invading pathogens. B. It creates memory cells for faster response upon re-exposure to invaders. C. It detects danger and activates the adaptive immune system by giving it permission to respond. D. It acts slowly but with high specificity to a wide variety of antigens.

31. What distinguishes the innate immune system from the adaptive immune system?

A. The innate system has highly diverse receptors specific to every pathogen B. The adaptive system acts faster than the innate system during infections C. The innate system uses receptors tuned to recognize common pathogens D. The adaptive system does not require activation to function

32. Which antibody class is most abundant in the blood serum and capable of crossing the placental barrier?

A. IgA B. IgE C. IgM D. IgG

33. What is the primary difference between class I and class II MHC molecules?

A. Class I are only found on immune cells; class II are on all body cells B. Class I present antigens to killer T cells; class II present antigens to helper T cells C. Class I molecules produce antibodies; class II molecules produce cytokines D. Class I trigger inflammation; class II cause cell death

34. What crucial function do cytokines secreted by helper T cells perform?

A. They directly neutralize pathogens B. They activate other immune cells to coordinate the immune response C. They present antigens to killer T cells D. They form the physical barrier against invaders

35. How does the innate immune system detect uncommon pathogens or abnormal cells?

A. Through specific antibody receptors B. Using specialized receptors tuned to detect danger molecules and signals from damaged cells C. By memory cells D. By constant phagocytosis of all cells

36. How do antibodies facilitate phagocytosis during an infection?

A. By producing enzymes that digest pathogens inside macrophages B. By binding antigens and connecting the pathogen to phagocytes via Fc receptors C. By triggering infected cells to self-destruct D. By neutralizing toxins without involving other cells

37. How do neutralizing antibodies prevent viruses from infecting cells?

A. By destroying viral DNA B. By binding the viral docking sites and preventing attachment to cellular receptors C. By killing virus-infected cells D. By breaking down viral proteins enzymatically

38. Which antibody class is the most abundant in human serum?

A. IgA B. IgG C. IgM D. IgE

39. Why is the two-key system important for helper T cell activation?

A. It ensures helper T cells do not activate without proper antigen recognition and co-stimulation B. It allows helper T cells to directly kill infected cells immediately C. It enables B cells to produce antibodies without T cell involvement D. It prevents any immune response to common pathogens

40. Why does the innate immune system “give permission” to the adaptive immune system to respond?

A. Because the adaptive system requires the innate system’s evaluation of danger signals to avoid attacking harmless molecules B. Because the adaptive immune system can only attack viruses and not bacteria C. Because the innate immune system can provide all defense without adaptive assistance D. Because the adaptive system works independently of pathogen recognition

41. Why do antibodies sometimes fail to completely neutralize viral infections?

A. Because antibodies cannot enter infected cells to kill viruses inside B. Because antibodies destroy only bacteria C. Because antibodies are not produced early enough D. Because viruses mutate too quickly

42. How long does the proliferation stage of T cell activation typically take?

A. A few hours B. About one day C. About a week D. Several weeks

43. What is the central regulator of innate and adaptive immune functions mentioned in the references?

A. NF-kappaB family of transcription factors B. Antibodies C. MHC molecules D. Cytokines

44. What role do cytokines play during bacterial infection?

A. Directly killing bacteria B. Acting as hormones to mediate communication between immune system cells C. Producing antibodies specific to the bacteria D. Presenting antigens to T cells

45. Which cells display Class II MHC molecules for activation of helper T cells?

A. Red blood cells B. All body cells C. Antigen-presenting cells (APCs) such as macrophages D. Killer T cells

46. What is the primary function of helper T cells?

A. Destroy infected cells directly B. Produce antibodies C. Secrete cytokines to activate other immune cells D. Engulf pathogens

47. What role does clonal selection play in adaptive immunity?

A. Creation of new antigen receptors randomly B. Proliferation of lymphocytes specific to an invading antigen C. Elimination of all self-reactive lymphocytes D. Memory cell activation during the first infection

48. How do macrophages identify invading bacteria?

A. By recognizing unique DNA sequences B. By sensing danger molecules such as bacterial membrane carbohydrates and fats C. Through antibody receptors only D. By recognizing viral particles

49. What is the second non-specific signal required to activate helper T cells?

A. Binding of antibody to antigen B. Interaction between B7 protein on APC and CD28 receptor on T cell C. Cytokine release from macrophages D. Phagocytosis of the antigen

50. Which cells are responsible for producing antibodies?

A. Helper T cells B. Macrophages C. B cells D. Natural killer cells