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What is the significance of HER2 positivity in breast cancer?
- A. Indicates aggressive tumor behavior and potential resistance to certain treatments
- B. Signifies slower tumor growth
- C. Indicates sensitivity to hormone therapy
- D. Denotes a benign tumor
Correct Answer: A
Rationale: HER2 positivity signifies aggressive tumor behavior and potential resistance to certain treatments, requiring targeted therapies.
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What was the important contribution to microbiology of Anton Van Leeuwenhoek in the 1600s?
- A. He was the first to observe microorganisms
- B. He disproved the theory of spontaneous generation of microorganisms
- C. He was the first to show that a disease could be caused by a microorganism
- D. He was the first to describe the process of fermentation
Correct Answer: A
Rationale: The correct answer is A: He was the first to observe microorganisms. Van Leeuwenhoek's important contribution to microbiology was his discovery of microorganisms using his own handcrafted microscopes. This observation revolutionized the field by providing the first direct evidence of the existence of microorganisms.
Choice B is incorrect because Leeuwenhoek's observations actually supported the idea of spontaneous generation. Choice C is incorrect because he did not link microorganisms to diseases. Choice D is incorrect because the process of fermentation was described by others before Leeuwenhoek.
What is included in the humoral immune response?
- A. Surveillance for malignant cell changes
- B. Production of antigen-specific immunoglobulins
- C. Direct attack of antigens by activated B lymphocytes
- D. Releasing cytokines responsible for destruction of antigens
Correct Answer: B
Rationale: The humoral immune response involves the production of antigen-specific antibodies (immunoglobulins) by B cells, which neutralize pathogens.
Which of the following is an example of passive immunization?
- A. The protection against smallpox that is provided by inoculation with cowpox
- B. The rapid protection that is provided by the primary immune response to a vaccine
- C. The immune protection provided to an individual after receiving serum from someone previously exposed to a pathogen
- D. Immunization of a child under the supervision of a parent or guardian
Correct Answer: C
Rationale: Passive immunization involves the transfer of pre-formed antibodies to confer immediate protection. Choice C is correct as it describes receiving serum containing antibodies from an immune individual. Choice A is incorrect because it describes active immunization. Choice B is incorrect as it refers to the primary immune response, which is part of active immunization. Choice D is incorrect as it describes the process of immunization itself, not passive immunization.
What is the process called when a specific lymphocyte binds its antigen and proliferates?
- A. Clonal deletion
- B. Clonal selection
- C. Antigen presentation
- D. Cytokine signaling
Correct Answer: B
Rationale: The correct answer is B: Clonal selection. During clonal selection, a specific lymphocyte recognizes its specific antigen, binds to it, and undergoes proliferation to generate a large population of identical cells to combat the antigen efficiently. This process ensures an effective immune response.
Incorrect choices:
A: Clonal deletion - This process involves the elimination of self-reactive lymphocytes to prevent autoimmunity, not the proliferation of antigen-specific lymphocytes.
C: Antigen presentation - This is the process by which antigens are displayed to immune cells for recognition, not the proliferation of lymphocytes.
D: Cytokine signaling - While cytokines play a role in immune responses, they are not directly involved in the proliferation of lymphocytes in response to specific antigens.
A co-receptor on target cells for HIV is
- A. gp120
- B. CR4
- C. CR5
- D. CXCR4
Correct Answer: D
Rationale: The correct answer is D: CXCR4. CXCR4 is a chemokine receptor that serves as a co-receptor for HIV entry into target cells. Step 1: HIV binds to CD4 receptor on the target cell. Step 2: The viral envelope protein gp120 then interacts with either CXCR4 or CCR5 co-receptor to facilitate viral entry. Step 3: In the case of CXCR4-tropic HIV strains, CXCR4 is the co-receptor used for entry into the target cell. Therefore, choice D is correct. Choices A (gp120) and C (CR5) are incorrect as they are not co-receptors, while choice B (CR4) is not a known co-receptor for HIV entry.