Nokea
What is a primary reason that the normal immune response fails to contain the HIV infection?
- A. CD4+ T cells become infected with HIV and are destroyed.
- B. The virus inactivates B cells, preventing the production of HIV antibodies.
- C. Natural killer cells are destroyed by the virus before the immune system can be activated.
- D. Monocytes ingest infected cells, differentiate into macrophages, and shed viruses in body tissues.
Correct Answer: A
Rationale: HIV specifically targets CD4+ T cells, depleting the immune system's ability to mount an effective response against pathogens.
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The activation of naïve T cells takes place in:
- A. Germinal centers
- B. Primary lymphoid tissues
- C. Secondary lymphoid tissues
- D. None of the above
Correct Answer: C
Rationale: The correct answer is C: Secondary lymphoid tissues. Naïve T cells are activated in secondary lymphoid tissues such as lymph nodes and spleen. These tissues are where T cells encounter antigen-presenting cells, receive co-stimulatory signals, and undergo clonal expansion to differentiate into effector T cells. Germinal centers are primarily for B cell responses. Primary lymphoid tissues (bone marrow and thymus) are where T cells mature but not where activation occurs. Choice D is incorrect as naïve T cell activation does occur in secondary lymphoid tissues.
Where and into what do activated B lymphocytes differentiate?
- A. Spleen; natural killer cells that destroy infected cells
- B. Bone marrow; plasma cells that secrete immunoglobulins
- C. Thymus; memory B-cells that retain a memory of the antigen
- D. Bursa of Fabricius; helper cells that in turn activate additional B lymphocytes
Correct Answer: B
Rationale: Activated B lymphocytes differentiate into plasma cells in the bone marrow, which produce and secrete antibodies.
The recirculation of naïve lymphocytes follows which sequential order?
- A. Blood, HEV, LN, efferent lymphatics, thoracic duct, blood
- B. Blood, afferent lymphatics, LN, thoracic duct, blood
- C. Inflammatory sites, afferent lymphatics, LN, efferent lymphatics, thoracic duct, blood
- D. Both A and C are correct
Correct Answer: A
Rationale: The correct answer is A because naïve lymphocytes circulate through blood, enter lymph nodes (LN) via high endothelial venules (HEV), encounter antigens in LN, exit via efferent lymphatics, drain into the thoracic duct, and return to blood circulation. Choice B is incorrect because it skips the step of entering LN through HEV. Choice C is incorrect because it starts with inflammatory sites instead of blood, and it also lacks the step of entering LN through HEV. Choice D is incorrect as only option A correctly follows the sequential order of recirculation of naïve lymphocytes.
What distinguishes adaptive immunity from innate immunity?
- A. It includes macrophages
- B. It is nonspecific and immediate
- C. It involves T and B lymphocytes
- D. It is based on physical barriers
Correct Answer: C
Rationale: The correct answer is C because adaptive immunity involves T and B lymphocytes that provide specific immune responses tailored to particular pathogens. T and B lymphocytes are key players in adaptive immunity, recognizing and targeting specific antigens. Choice A is incorrect because macrophages are part of innate immunity. Choice B is incorrect because innate immunity is nonspecific and immediate, while adaptive immunity is specific and takes time to develop. Choice D is incorrect because physical barriers are a characteristic of innate immunity, not adaptive immunity.
Determine the following diseases that are not thought to be an autoimmune disease.
- A. Rheumatoid arthritis
- B. Multiple sclerosis
- C. Cancer of the bone marrow
- D. Insulin-dependent diabetes
Correct Answer: C
Rationale: The correct answer is C, Cancer of the bone marrow. Autoimmune diseases occur when the immune system mistakenly attacks healthy cells. Rheumatoid arthritis, multiple sclerosis, and insulin-dependent diabetes are autoimmune diseases where the immune system targets specific tissues or organs. Cancer of the bone marrow, on the other hand, is a result of uncontrolled cell growth and division, not a malfunction of the immune system attacking the body's own tissues. Therefore, it is not considered an autoimmune disease.