Nokea
The basic structure of an antibody molecule is
- A. One light chain and one heavy chain that are covalently linked and form one antigen binding site
- B. Two identical heavy chains and two identical light chains that are covalently linked and form two antigen binding sites
- C. Two identical heavy chains and two identical light chains covalently linked to form one antigen binding site
- D. Two identical light chains that form the antigen binding site and two identical heavy chains that mediate the effector functions of antibodies
Correct Answer: B
Rationale: Rationale for Answer B:
1. Antibody structure consists of two identical heavy chains and two identical light chains.
2. These chains are covalently linked to form the Y-shaped structure of an antibody.
3. Each chain contributes to the formation of antigen-binding sites.
4. Therefore, two identical heavy chains and two identical light chains form two antigen-binding sites.
Summary of Incorrect Choices:
A: Incorrect because it describes only one antigen-binding site formed by one light chain and one heavy chain.
C: Incorrect because it describes one antigen-binding site formed by two identical heavy chains and two identical light chains.
D: Incorrect because it incorrectly describes the roles of light and heavy chains in antibody structure.
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What is the outcome of clonal selection after a lymphocyte is activated?
- A. Cytokine suppression
- B. Formation of memory and effector cells
- C. Antigen elimination without cellular proliferation
- D. Destruction of the lymphocyte
Correct Answer: B
Rationale: The correct answer is B because clonal selection during lymphocyte activation leads to the formation of memory and effector cells. This process involves the proliferation and differentiation of the activated lymphocyte into these specialized cells, which play crucial roles in immune responses upon encountering the same antigen in the future. Cytokine suppression (choice A) is not the direct outcome of clonal selection but may be a regulatory mechanism during immune responses. Antigen elimination without cellular proliferation (choice C) is not accurate as clonal selection involves the expansion of specific lymphocyte clones. Destruction of the lymphocyte (choice D) is not the outcome of clonal selection, as activated lymphocytes undergo proliferation and differentiation rather than destruction.
Which one of the following processes emerged earliest during the course of evolution?
- A. Antigen presentation
- B. Antibody production
- C. Phagocytosis
- D. Thymic education
Correct Answer: C
Rationale: The correct answer is C: Phagocytosis. Phagocytosis is a fundamental process that emerged early in evolution for cellular organisms to engulf and digest particles. This process is essential for basic survival and defense mechanisms.
A: Antigen presentation and B: Antibody production are more advanced immune responses that occur in higher organisms and require a complex immune system.
D: Thymic education is a process specific to vertebrates involving the maturation and selection of T cells, which is a more evolved mechanism compared to phagocytosis.
Therefore, phagocytosis is the earliest process among the options listed as it is essential for basic cellular survival and predates the development of advanced immune responses.
You give an intradermal injection of allergen to a patient who is undergoing skin testing for allergies. A few minutes later,the patient complains about feeling anxious short of breath and dizzy. You notice that the patient has reddened blotches on the face and arms. All of these therapies are available on your emergency cart. Which action should you take first?
- A. Start oxygen at 4 L/min using a nasal cannula.
- B. Obtain IV access with a large-bore IV catheter.
- C. Administer epinephrine (Adrenalin) 0.3 mL subcutaneously.
- D. Give albuterol (Proventil) with a nebulizer.
Correct Answer: C
Rationale: The patient is showing signs of anaphylaxis,a life-threatening allergic reaction. The first priority is to administer epinephrine which acts quickly to reverse the symptoms by constricting blood vessels relaxing airway muscles and increasing heart rate. Oxygen and IV access are important but secondary to the immediate administration of epinephrine. Albuterol may be used for bronchospasm but is not the first-line treatment for anaphylaxis.
Factors important in the eradication of smallpox include
- A. Smallpox is a human pathogen; it is not found in animals.
- B. The vaccine was easily delivered and did not require sophisticated materials or technical skills
- C. The disease is contagious only when the symptoms are manifest making isolation an effective measure
- D. All of the above is correct
Correct Answer: D
Rationale: The correct answer is D because all the factors mentioned are important in the eradication of smallpox. A is correct because smallpox is specific to humans, simplifying eradication efforts. B is correct as the vaccine was easily deployable. C is correct as isolation of symptomatic individuals helped control the spread. Therefore, all choices are important in the successful eradication of smallpox.
Which of the following causes memory cells to convert to plasma cells?
- A. An organ transplant
- B. Release of lymphokines
- C. Re-exposure to a specific antigen
- D. Initial exposure to an antigen
Correct Answer: C
Rationale: Memory cells convert to plasma cells upon re-exposure to a specific antigen which triggers a rapid and robust immune response.