Nokea
Epithelial cells at mucosal sites have barrier functions exerted through several mechanisms. These mechanisms do not include:
- A. Secretion of mucins
- B. Secretion of antimicrobial peptides
- C. Phagocytosis of microbes
- D. Tight junctions
Correct Answer: C
Rationale: The correct answer is C: Phagocytosis of microbes. Epithelial cells primarily act as a physical barrier to prevent the entry of microbes. Phagocytosis is a function of immune cells, not epithelial cells. A: Secretion of mucins helps trap pathogens. B: Secretion of antimicrobial peptides aids in defense. D: Tight junctions form a physical barrier between cells. Therefore, phagocytosis is not a direct mechanism exerted by epithelial cells at mucosal sites.
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The adaptive immune response:
- A. Is dependent on the innate immune response for initiation
- B. Involves both humoral and cell-mediated responses
- C. Provides cytokines that influence the response of innate cells, i.e. macrophages
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because the adaptive immune response relies on the initiation by the innate immune response (A), involves both humoral (antibody production) and cell-mediated (T cell activation) responses (B), and produces cytokines that can modulate the activity of innate immune cells like macrophages (C). Therefore, all of the statements are true regarding the adaptive immune response, making option D the correct choice.
Which of the following is NOT part of innate immunity?
- A. Cytokine secretion
- B. Natural killer (NK) cell activity
- C. B cell antibody production
- D. Phagocytosis by macrophages
Correct Answer: C
Rationale: Answer C is correct because B cell antibody production is part of adaptive immunity, not innate immunity. Innate immunity is the body's first line of defense and includes mechanisms like cytokine secretion, NK cell activity, and phagocytosis by macrophages. B cells are part of the adaptive immune response, producing antibodies specific to pathogens upon exposure. This distinction is crucial in understanding the different roles innate and adaptive immunity play in protecting the body.
Innate behaviors are
- A. under strong genetic control
- B. performed in virtually the indifferent way by all individuals of a species
- C. Sociobiology
- D. the environment
Correct Answer: A
Rationale: The correct answer is A because innate behaviors are indeed under strong genetic control. These behaviors are instinctual and are genetically programmed in organisms. This genetic control ensures that all individuals of a species exhibit these behaviors consistently. Choice B is incorrect because while innate behaviors may be performed similarly by individuals of a species, there can still be variations. Choice C, Sociobiology, is incorrect as it is a branch of biology that studies social behavior in animals. Choice D, the environment, is incorrect as innate behaviors are not primarily influenced by the environment but rather by genetic factors.
Which of the following is not required for full activation of a naïve lymphocyte?
- A. Migration into an inflammatory site
- B. Costimulatory signalling
- C. Cytokines
- D. Recognition of specific antigen
Correct Answer: A
Rationale: The correct answer is A. Naïve lymphocytes require activation through recognition of specific antigen, costimulatory signaling, and cytokines. Migration into an inflammatory site is not a requirement for full activation. Naïve lymphocytes can be activated in secondary lymphoid organs where antigen presentation occurs. Migration to inflammatory sites occurs after activation to fight infections.
Which of the following statements best characterizes an antibody?
- A. An antibody contains high molecular weight RNA as its basic structure.
- B. An antibody is composed of protein and cannot be distinguished from the albumin fraction of the serum proteins.
- C. An antibody is composed of four identical protein subunits which may be caused to dissociate by treatment with urea.
- D. An antibody contains protein as its major chemical component and its synthesis may be elicited by the administration of a foreign protein or polysaccharide.
Correct Answer: D
Rationale: Rationale for Correct Answer D:
1. Antibodies are composed mainly of proteins, specifically immunoglobulins.
2. Antibodies are synthesized in response to foreign proteins or polysaccharides, known as antigens.
3. This process involves B cells recognizing antigens and producing antibodies.
4. The statement accurately reflects the nature of antibody structure and synthesis.
Summary of Incorrect Choices:
A: Antibodies do not contain RNA as their basic structure; they are primarily composed of proteins.
B: Antibodies can be distinguished from albumin fraction as they have specific functions in the immune system.
C: Antibodies consist of two heavy and two light chains, not four identical protein subunits, and are not typically dissociated by urea.