Nokea
What is the primary role of Helper T cells in the immune response?
- A. Killing infected host cells
- B. Producing antibodies
- C. Secreting cytokines to activate other immune cells
- D. Suppressing immune responses
Correct Answer: C
Rationale: Helper T cells primarily secrete cytokines to activate other immune cells. This is crucial for coordinating and amplifying the immune response. They do not kill infected host cells (A), as that is the role of cytotoxic T cells. Producing antibodies (B) is the function of B cells. Suppressing immune responses (D) is the role of regulatory T cells, not Helper T cells.
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Which of the following statements is NOT true
- A. Light chains isotypes are functionally different
- B. The antigen binding site of a B cell receptor is identical to the antigen binding site of antibodies secreted by the same B cell
- C. Both heavy and light chain domains assume a compact barrel structure
- D. The hinge region assumes a more open and flexible structure
Correct Answer: A
Rationale: The correct answer is A: Light chains isotypes are functionally different. This statement is NOT true because light chain isotypes (kappa and lambda) have distinct primary structures but serve the same function in antigen binding. The heavy chain determines the effector function of antibodies. The other choices are correct: B) The antigen binding site of a B cell receptor is identical to the antigen binding site of antibodies secreted by the same B cell, as both use the same variable regions for antigen recognition. C) Both heavy and light chain domains assume a compact barrel structure, which is essential for antibody stability and function. D) The hinge region assumes a more open and flexible structure, allowing antibodies to bind antigens at different orientations.
Lysozyme is NOT
- A. An enzyme present in secretions and tears
- B. A type of Defensin
- C. Part of the chemical innate barriers to infection
- D. A protein capable of dissolving the cell wall of bacteria
Correct Answer: B
Rationale: The correct answer is B because lysozyme is not a type of defensin. Lysozyme is an enzyme present in secretions and tears, part of chemical innate barriers to infection, and capable of dissolving the cell wall of bacteria. Defensins are a different type of antimicrobial peptides that function by disrupting the microbial cell membrane. Therefore, B is the correct answer as it does not accurately describe lysozyme's function.
The nurse is studying hypersensitivity reactions. Which reactions are correctly matched with their hypersensitivity types? (Select one that does not apply.)
- A. Type I—examples include hay fever and anaphylaxis.
- B. Type II—mediated by action of immunoglobulin M (IgM).
- C. Type III—immune complex deposits in blood vessel walls.
- D. Type IV—examples are poison ivy and transplant rejection.
Correct Answer: B
Rationale: The correct answer is B because Type II hypersensitivity reactions are mediated by the action of immunoglobulin G (IgG) or immunoglobulin M (IgM), not just IgM alone. IgG or IgM antibodies target specific antigens on the surface of cells or tissues, leading to cell destruction. In contrast, Type I hypersensitivity reactions (choice A) involve immediate IgE-mediated responses to allergens like hay fever and anaphylaxis. Type III reactions (choice C) are characterized by immune complex deposition in tissues, not blood vessel walls. Type IV reactions (choice D) are delayed hypersensitivity reactions involving T cell-mediated responses, such as poison ivy contact dermatitis and transplant rejection.
Which of the following statement is incorrect
- A. Antigens in tissues can reach regional LN via afferent lymphatic vessels
- B. Migrating dendritic cells that have collected antigens in tissues enter the draining LN via HEV
- C. During an infection fever and other inflammatory signals induce increased blood flow to draining LN and increased chances for lymphocytes to migrate from blood into LN
- D. The thoracic duct returns most of the circulating lymphocytes back to blood
Correct Answer: B
Rationale: The correct answer is B because migrating dendritic cells do not enter the draining lymph node (LN) via high endothelial venules (HEV); instead, they enter through afferent lymphatic vessels. HEVs are specialized post-capillary venules in LN where lymphocytes enter from the bloodstream. Dendritic cells, carrying antigens from tissues, travel via afferent lymphatic vessels to reach the LN where they present antigens to lymphocytes. Option A is correct as antigens in tissues reach LN via afferent lymphatic vessels. Option C is correct as infection-induced signals can increase blood flow to LN, facilitating lymphocyte migration. Option D is incorrect because the thoracic duct returns lymph back to the bloodstream, not specifically lymphocytes.
One principal function of the Class I and Class II major histocompatibility complex S proteins is to
- A. transduce the signal to the T-cell interior following antigen binding
- B. mediate immunoglobulin class switching
- C. present antigen for recognition by the T-cell antigen receptor
- D. stimulate production of interleukins
Correct Answer: C
Rationale: The correct answer is C because Class I and Class II MHC proteins present antigens to T-cell receptors for immune response activation. Class I MHC presents endogenous antigens to CD8+ T cells, while Class II MHC presents exogenous antigens to CD4+ T cells. Choice A is incorrect because MHC proteins do not transduce signals. Choice B is incorrect because MHC proteins do not mediate immunoglobulin class switching. Choice D is incorrect because MHC proteins do not directly stimulate interleukin production.