Nokea
T regulatory cells are NOT
- A. Generated in the thymus upon expression of Foxp3
- B. Generated in the periphery in response to cytokines
- C. Able to inhibit effector T cells
- D. Able to cause immunity
Correct Answer: D
Rationale: The correct answer is D because T regulatory cells are known to suppress immune responses and promote immune tolerance, which is opposite to causing immunity. Choice A is incorrect because T regulatory cells are indeed generated in the thymus upon expression of Foxp3. Choice B is incorrect as T regulatory cells can also be generated in the periphery in response to cytokines. Choice C is incorrect as T regulatory cells are known to inhibit effector T cells to regulate immune responses.
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What is the main purpose of complement component C5a?
- A. Opsonization
- B. Cell lysis
- C. Recruitment and activation of immune cells
- D. Inhibition of inflammation
Correct Answer: C
Rationale: The correct answer is C: Recruitment and activation of immune cells. C5a is a potent chemoattractant that attracts immune cells to the site of infection or inflammation. It also activates these immune cells, leading to enhanced immune responses. Option A (Opsonization) and B (Cell lysis) are not the main functions of C5a. Option D (Inhibition of inflammation) is incorrect because C5a actually promotes inflammation by recruiting and activating immune cells.
What is the primary goal of palliative care in cancer treatment?
- A. Cure the disease
- B. Extend life expectancy
- C. Relieve suffering and improve quality of life
- D. Prevent disease recurrence
Correct Answer: C
Rationale: Palliative care focuses on relieving suffering and improving quality of life for patients with advanced cancer.
The reason for using Taq polymerase for PCR is that
- A. it has regions that are complementary to primers.
- B. only minute amounts are needed for each cycle of PCR
- C. it binds more readily than other polymerases to primer.
- D. it is heat stable and can withstand the temperature changes of the cycler.
Correct Answer: D
Rationale: The correct answer is D because Taq polymerase is heat-stable, allowing it to withstand the high temperatures used in PCR cycles without denaturing. This heat stability is crucial for the repeated heating and cooling cycles in PCR. Choice A is incorrect because Taq polymerase does not need to be complementary to primers. Choice B is incorrect because the amount needed is not the main reason for using Taq polymerase. Choice C is incorrect because binding affinity to primers is not the primary reason for using Taq polymerase.
Severe combined immunodeficiency (SCID) is a disease caused by:
- A. Infection with human immunodeficiency virus
- B. One of several inherited genetic mutations
- C. Deficiency of both innate and adaptive immune components
- D. Deficiency of hematopoietic stem cells
Correct Answer: B
Rationale: Step 1: SCID is a genetic disorder affecting the immune system.
Step 2: Inherited genetic mutations cause abnormalities in immune cells.
Step 3: These mutations lead to severe deficiencies in immune function.
Step 4: Choice B accurately reflects the genetic basis of SCID.
Summary: Choice A is incorrect because SCID is not caused by HIV. Choice C is incorrect as it oversimplifies the immune deficiencies in SCID. Choice D is incorrect because SCID primarily affects immune cells, not stem cells.
With regard to NADPH oxidase, which of the following statements in not correct?
- A. It is the enzyme involved in the respiratory burst that follows the engagement of phagocytic receptors
- B. Individuals with mutations of NADPH oxidase subunits suffer repeated infections because of defective killing of phagocytosed pathogens
- C. It is constitutively expressed as a complex of 5 subunits in unstimulated cells
- D. It controls the formation of reactive oxygen species
Correct Answer: C
Rationale: The correct answer is C because NADPH oxidase is not constitutively expressed as a complex of 5 subunits in unstimulated cells. Instead, it is assembled and activated upon stimulation, such as during the respiratory burst following phagocytosis. Choice A is correct as NADPH oxidase is indeed involved in the respiratory burst. Choice B is correct as mutations in NADPH oxidase subunits lead to impaired pathogen killing and recurrent infections. Choice D is correct as NADPH oxidase controls the production of reactive oxygen species.