Adaptive Immune System Quizlet

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Which of the following is a safety mechanism of the complement system?

  • A. Binding C5a to plasma inhibitors
  • B. Activation of complement only in the absence of pathogens
  • C. Covalent binding of C3b and C4b to pathogen surfaces
  • D. Suppression of C1 activation by antibodies
Correct Answer: C

Rationale: Rationale for Choice C: Covalent binding of C3b and C4b to pathogen surfaces is a safety mechanism of the complement system because it helps in targeting pathogens specifically, enhancing opsonization, and preventing damage to host cells by limiting complement activation to the pathogen surface. C3b and C4b form stable covalent bonds with the pathogens, marking them for destruction by phagocytes. This mechanism ensures that complement activation is directed towards the pathogen and not host cells, thus maintaining immune homeostasis.

Summary:
A: Binding C5a to plasma inhibitors is not a safety mechanism but a regulatory mechanism in the complement system.
B: Activation of complement only in the absence of pathogens is incorrect as the complement system can be activated in response to various stimuli, not just pathogens.
D: Suppression of C1 activation by antibodies is not a safety mechanism but a regulatory mechanism involving the classical pathway of complement activation.

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Which of the following is a feature of an adaptive immune response

  • A. Triggered within minutes/hours of antigen exposure
  • B. Present in all multicellular organisms
  • C. Results in the induction of memory of previously encountered antigens
  • D. Always able to discriminate self from non-self in all individuals
Correct Answer: C

Rationale: The correct answer is C because an adaptive immune response induces memory of previously encountered antigens. This memory allows the immune system to respond more rapidly and effectively upon subsequent exposures to the same antigen. This feature is crucial for long-term immunity. Option A is incorrect since adaptive immune responses typically take days to develop. Option B is incorrect as not all multicellular organisms possess adaptive immunity. Option D is incorrect because immune tolerance mechanisms can sometimes fail, leading to autoimmune disorders where self is not distinguished from non-self.

Which cytokine category is associated with tumor necrosis factors?

  • A. Interleukins
  • B. Interferons
  • C. TNF-alpha and TNF-beta
  • D. TGF-beta
Correct Answer: C

Rationale: The correct answer is C: TNF-alpha and TNF-beta. Tumor necrosis factors (TNF) are a specific category of cytokines known for their role in promoting inflammation and inducing cell death in tumor cells. TNF-alpha and TNF-beta are two key members of this cytokine category. Interleukins (choice A) are a different group of cytokines involved in immune responses. Interferons (choice B) are cytokines that help regulate the immune system's response to viral infections. TGF-beta (choice D) is a cytokine involved in regulating cell growth and differentiation, but not specifically associated with tumor necrosis factors.

Defensins are

  • A. Cationic antimicrobial peptides
  • B. Opsonins
  • C. DAMPs
  • D. Fatty acids
Correct Answer: A

Rationale: Defensins are cationic antimicrobial peptides that play a crucial role in the innate immune system by disrupting the microbial cell membrane. This property allows them to kill a wide range of pathogens. Option A is correct because it accurately describes the primary function of defensins.
Option B, opsonins, are proteins that enhance phagocytosis but are not specific to defensins. Option C, DAMPs, are damage-associated molecular patterns released by damaged cells and are not related to defensins. Option D, fatty acids, are not directly related to the antimicrobial properties of defensins.

What is the diversity of pattern recognition receptors (PRRs) like?

  • A. Highly diverse due to somatic recombination
  • B. Limited because they are germline-encoded
  • C. Constantly changing in response to infections
  • D. Specific to individual antigens
Correct Answer: B

Rationale: The correct answer is B because pattern recognition receptors (PRRs) are encoded in the germline, meaning they are genetically determined and do not change during an individual's lifetime. This ensures consistency in detecting various pathogens across different individuals. Choices A, C, and D are incorrect because PRR diversity is not influenced by somatic recombination, does not change constantly in response to infections, and is not specific to individual antigens.

Molecules that are considered members of the 'immunoglobulin superfamily':

  • A. Contain one or more protein domains with a compact barrel structure
  • B. Are always lymphocyte antigen receptors
  • C. Are highly unstable relative to other proteins
  • D. All of the above
Correct Answer: A

Rationale: The correct answer is A because molecules in the immunoglobulin superfamily typically contain one or more protein domains with a compact barrel structure. This structure is characteristic of immunoglobulin-like domains found in proteins involved in immune responses. Choice B is incorrect because not all members of the immunoglobulin superfamily are lymphocyte antigen receptors. Choice C is incorrect as these molecules are not necessarily highly unstable compared to other proteins. Therefore, the correct answer is A as it accurately describes a common structural feature of molecules in the immunoglobulin superfamily.

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