Nokea
In LN naïve T cells and activated dendritic cells interact in the
- A. Subcapsular sinus
- B. Cortex
- C. Paracortex
- D. Medulla
Correct Answer: C
Rationale: The correct answer is C: Paracortex. Naïve T cells circulate through the blood and lymphatic system until they encounter antigens presented by activated dendritic cells in the paracortex of lymph nodes. The paracortex is the region where T cell activation and proliferation occur, leading to an immune response. The subcapsular sinus (A) is primarily involved in filtering lymph fluid, the cortex (B) contains B cell follicles, and the medulla (D) contains plasma cells and macrophages. Thus, the paracortex is the specific site of interaction between naïve T cells and activated dendritic cells in lymph nodes.
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A 69-year-old woman asks the nurse whether it is possible to 'catch' cancer because many of her friends of the same age have been diagnosed with different kinds of cancer. In responding to the woman, the nurse understands that what factor increases the incidence of tumors in older adults?
- A. An increase in autoantibodies
- B. Decreased activity of the bone marrow
- C. Decreased differentiation of T lymphocytes
- D. Decreased size and activity of the thymus gland
Correct Answer: D
Rationale: The thymus gland shrinks with age, reducing the production of new T cells, which impairs immune surveillance and increases cancer risk.
Which of the following statements concerning Influenza Hemagglutinin (HA) and Neuraminidase (N) is incorrect
- A. Both mutate frequently due to antigenic drift
- B. Function of N is to release new viral particles from infected cells
- C. HA binds to terminal sialic acid on cell surface molecules found on lung epithelial cells
- D. Tamiflu interferes with the attachment of HA to sialic acid
Correct Answer: D
Rationale: The correct answer is D. Tamiflu interferes with the function of Neuraminidase (N), not Hemagglutinin (HA). HA binds to sialic acid on cell surface molecules, not N. N's function is to release new viral particles. Both HA and N undergo antigenic drift. Therefore, choice D is incorrect as it misrepresents the mechanism of action of Tamiflu.
Lysozyme
- A. Helps protecting the eye from pathogens
- B. Is a cationic protein able to bind the negatively charged membrane of bacteria
- C. Can digest the cell wall of bacteria
- D. Is a MAMP
Correct Answer: D
Rationale: Firstly, Lysozyme is a Microbe-Associated Molecular Pattern (MAMP), not a protein. MAMPs are molecules recognized by the innate immune system to trigger immune responses. Lysozyme is not specific to protecting the eye (A), binding membranes (B), or digesting cell walls (C). Therefore, the correct answer is D.
Which of the following statements is true?
- A. MHC class I and MHC class II molecules both consist of two transmembrane protein chains
- B. MHC class I molecules have one peptide-binding site whereas MHC class II molecules have two peptide-binding sites
- C. A given MHC molecule binds only one peptide at a time
- D. MHC molecules on the cell surface have empty peptide-binding sites in the absence of infection
Correct Answer: C
Rationale: The correct answer is C because a given MHC molecule can bind only one peptide at a time. This is essential for the proper presentation of antigens to immune cells. MHC class I and class II molecules do not consist of two transmembrane protein chains (A), MHC class I molecules have one peptide-binding site while MHC class II molecules have one peptide-binding site (B), and MHC molecules on the cell surface typically have peptides bound to their peptide-binding sites, even in the absence of infection (D).
What distinguishes Type V hypersensitivity from Type II?
- A. It is mediated by T cells
- B. Antibodies stimulate receptors instead of destroying them
- C. It involves immune complex formation
- D. It does not involve the immune system
Correct Answer: B
Rationale: The correct answer is B because Type V hypersensitivity involves antibodies stimulating receptors instead of destroying them. In Type II hypersensitivity, antibodies target antigens on cell surfaces, leading to cell destruction. In Type V, antibodies bind to cell receptors, causing abnormal receptor activation. Choices A, C, and D are incorrect because Type V hypersensitivity is not mediated by T cells (A), does not involve immune complex formation (C), and does involve the immune system (D). Therefore, the unique characteristic of Type V hypersensitivity is the stimulation of receptors by antibodies, making choice B the correct answer.