What are the two main outcomes of clonal selection?
- A. T cell activation and cytokine suppression
- B. Differentiation into effector and memory cells
- C. Pathogen destruction and tissue repair
- D. Phagocytosis and complement activation
Correct Answer: B
Rationale: The correct answer is B: Differentiation into effector and memory cells. During clonal selection, activated lymphocytes undergo differentiation into effector cells that combat the current infection and memory cells that provide long-lasting immunity. Effector cells directly eliminate pathogens, while memory cells remember the specific pathogen for future encounters. Choices A, C, and D are incorrect as they do not accurately represent the main outcomes of clonal selection. T cell activation and cytokine suppression (A) are processes involved in immune response regulation rather than the direct outcomes of clonal selection. Pathogen destruction and tissue repair (C) are broader immune responses that occur after clonal selection. Phagocytosis and complement activation (D) involve innate immune responses, not the adaptive immune responses seen in clonal selection.
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The discovery of immunoglobulin gene rearrangement helped to explain:
- A. How the number of different immunoglobulins produced by an individual can be far greater than the number of genes in the human genome
- B. How the number of genes in the human genome can be far greater than the number of different immunoglobulins produced by an individual
- C. How thousands of immunoglobulin chains of different sequence may be produced by a single B cell
- D. Both A and C are correct
Correct Answer: A
Rationale: The correct answer is A: How the number of different immunoglobulins produced by an individual can be far greater than the number of genes in the human genome. Immunoglobulin gene rearrangement occurs during B cell development, leading to the generation of a diverse repertoire of antibodies from a limited number of genes. This process allows for the production of a vast array of immunoglobulins through mechanisms like V(D)J recombination. Choice B is incorrect because the gene rearrangement process actually enables a single gene to encode for multiple immunoglobulins. Choice C is partially correct but does not fully capture the significance of gene rearrangement in expanding the diversity of immunoglobulins beyond what the genome would suggest. Choice D is incorrect as it combines a correct statement (A) with an incomplete statement (C).
The patient was told she has carcinoma in situ, and the student nurse wonders what that is. How should the nurse explain this to the student nurse?
- A. Evasion of the immune system by cancer cells
- B. Lesion with histologic features of cancer except invasion
- C. Capable of causing cellular alterations associated with cancer
- D. Tumor cell surface antigens that stimulate an immune response
Correct Answer: B
Rationale: Carcinoma in situ refers to a lesion with histologic features of cancer but without invasion into surrounding tissues.
Which molecule released by NK cells is responsible for inducing apoptosis?
- A. Perforin
- B. Granzyme
- C. Cytokines
- D. Antibodies
Correct Answer: B
Rationale: The correct answer is B: Granzyme. Granzyme is the molecule released by NK cells that induces apoptosis in target cells. It enters the target cell through perforin, which creates pores in the target cell membrane. Cytokines are signaling molecules released by various immune cells but do not directly induce apoptosis. Antibodies are produced by B cells and do not induce apoptosis. Perforin aids in the delivery of granzyme but is not responsible for inducing apoptosis itself. Therefore, Granzyme is the correct choice for inducing apoptosis by NK cells.
All of the following are true with respect to IgM antibodies EXCEPT which one
- A. they fix complement
- B. they occur on the surface of lymphocytes
- C. they predominate in the primary response to antigen
- D. mediate allergic reactions
Correct Answer: D
Rationale: The correct answer is D. IgM antibodies do not mediate allergic reactions. IgE antibodies are responsible for allergic reactions. IgM antibodies fix complement, occur on the surface of lymphocytes, and predominate in the primary response to antigens. IgM is the first antibody produced in response to an infection, playing a key role in the activation of the complement system. IgM antibodies are mainly found in the blood and lymphatic system, not on the surface of lymphocytes. IgE antibodies are the primary mediators of allergic reactions by triggering the release of histamine and other inflammatory molecules.
Which pathway of the complement system involves properdin, Factor B, and Factor D?
- A. Classical pathway
- B. Alternative pathway
- C. Lectin pathway
- D. Terminal pathway
Correct Answer: B
Rationale: The correct answer is B: Alternative pathway. This pathway involves properdin, Factor B, and Factor D. Properdin stabilizes the C3 convertase complex formed by Factor B and Factor D, leading to the amplification of the complement cascade. The other choices are incorrect because:
A: Classical pathway is initiated by antigen-antibody complexes binding to C1q.
C: Lectin pathway is activated by lectins binding to carbohydrates on pathogen surfaces.
D: Terminal pathway involves the formation of the membrane attack complex.