Nokea
Which of the following processes does not require the involvement of an antigen-specific T helper cell?
- A. Somatic hypermutation
- B. VDJ gene rearrangement
- C. Immunoglobulin class switching
- D. Memory cell differentiation
Correct Answer: B
Rationale: Correct Answer: B (VDJ gene rearrangement)
Rationale:
1. VDJ gene rearrangement occurs during B cell development in the bone marrow, independent of T helper cells.
2. Somatic hypermutation and immunoglobulin class switching require T helper cell interactions.
3. Memory cell differentiation also involves T helper cells for activation and differentiation.
4. Therefore, VDJ gene rearrangement is the only process not directly dependent on antigen-specific T helper cells.
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Which of the following is a safety mechanism of the complement system?
- A. Binding C5a to plasma inhibitors
- B. Activation of complement only in the absence of pathogens
- C. Covalent binding of C3b and C4b to pathogen surfaces
- D. Suppression of C1 activation by antibodies
Correct Answer: C
Rationale: Rationale for Choice C: Covalent binding of C3b and C4b to pathogen surfaces is a safety mechanism of the complement system because it helps in targeting pathogens specifically, enhancing opsonization, and preventing damage to host cells by limiting complement activation to the pathogen surface. C3b and C4b form stable covalent bonds with the pathogens, marking them for destruction by phagocytes. This mechanism ensures that complement activation is directed towards the pathogen and not host cells, thus maintaining immune homeostasis.
Summary:
A: Binding C5a to plasma inhibitors is not a safety mechanism but a regulatory mechanism in the complement system.
B: Activation of complement only in the absence of pathogens is incorrect as the complement system can be activated in response to various stimuli, not just pathogens.
D: Suppression of C1 activation by antibodies is not a safety mechanism but a regulatory mechanism involving the classical pathway of complement activation.
Which cytokine category is associated with tumor necrosis factors?
- A. Interleukins
- B. Interferons
- C. TNF-alpha and TNF-beta
- D. TGF-beta
Correct Answer: C
Rationale: The correct answer is C: TNF-alpha and TNF-beta. Tumor necrosis factors (TNF) are a specific category of cytokines known for their role in promoting inflammation and inducing cell death in tumor cells. TNF-alpha and TNF-beta are two key members of this cytokine category. Interleukins (choice A) are a different group of cytokines involved in immune responses. Interferons (choice B) are cytokines that help regulate the immune system's response to viral infections. TGF-beta (choice D) is a cytokine involved in regulating cell growth and differentiation, but not specifically associated with tumor necrosis factors.
Cardiac output
- A. coronary insufficient circulation
- B. A defect in one or more heart valves
- C. Disorder in a heartbeat
- D. Amount of blood/minute pumped into systemic circuit
Correct Answer: D
Rationale: The correct answer is D because cardiac output refers to the amount of blood pumped by the heart into the systemic circulation per minute. It is a crucial measure of heart function. Option A, coronary insufficient circulation, specifically refers to inadequate blood flow to the heart muscle itself, not overall cardiac output. Option B, a defect in heart valves, would affect the efficiency of blood flow but not necessarily the total amount of blood pumped. Option C, a disorder in heart rhythm, relates to irregular heartbeat patterns rather than the volume of blood pumped. Therefore, D is the correct choice as it directly relates to the definition of cardiac output.
Which type of immunity is the result of contact with the antigen through infection and is the longest lasting type of immunity?
- A. Active innate immunity
- B. Passive innate immunity
- C. Active acquired immunity
- D. Passive acquired immunity
Correct Answer: C
Rationale: Active acquired immunity results from direct exposure to an antigen, such as through infection or vaccination. It involves the body's immune system recognizing and remembering the antigen, leading to long-lasting immunity.
Which patient is at risk for hypernatremia?
- A. Has a deficiency of aldosterone
- B. Has prolonged vomiting and diarrhea
- C. Receives excessive IV 5% dextrose solution
- D. Has impaired consciousness and decreased thirst sensitivity
Correct Answer: D
Rationale: Impaired consciousness leads to decreased thirst sensitivity, preventing adequate water intake and increasing sodium concentration in the blood.