Nokea
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.
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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.
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.
Ribosomes associated with cells or organelles have a certain size, which is expressed in Svedberg units. Which associations are incorrect?
- A. cyanobacteria - 80s
- B. chloroplasts - 60s
- C. photosynthetic bacteria - 80s
- D. green algal cytoplasm - 80s
Correct Answer: A
Rationale: The correct answer is A because cyanobacteria have ribosomes measured in 70s, not 80s. Ribosomes in prokaryotes are either 70s (composed of 50s and 30s subunits) or 80s in eukaryotes (60s and 40s subunits). Choices B, C, and D are incorrect because chloroplasts, photosynthetic bacteria, and green algal cytoplasm all have ribosomes measured in 70s or 80s, consistent with their cell types.
A hybridoma:
- A. Secretes both polyclonal and monoclonal antibodies
- B. Is generated from the fusion of two antigen-activated B cells
- C. Can live in tissue culture indefinitely
- D. All of these options describe a hybridoma
Correct Answer: C
Rationale: Step-by-step rationale:
1. Hybridoma is a cell line formed by the fusion of a B cell (producing a specific antibody) and a myeloma cell.
2. Choice C is correct because hybridomas can be immortalized and cultured indefinitely.
3. Choice A is incorrect because hybridomas produce monoclonal antibodies, not polyclonal antibodies.
4. Choice B is incorrect because hybridomas are formed from a single B cell and a myeloma cell, not two antigen-activated B cells.
5. Choice D is incorrect as only option C accurately describes a hybridoma's characteristic of indefinite tissue culture survival.
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.