Nokea
Which of the following is a physical barrier provided by innate immunity?
- A. Antibodies
- B. T lymphocytes
- C. Tight junctions in epithelial cells
- D. Phagocytosis
Correct Answer: C
Rationale: The correct answer is C: Tight junctions in epithelial cells. These junctions physically prevent pathogens from entering the body. Antibodies (A) and T lymphocytes (B) are components of adaptive immunity, not physical barriers. Phagocytosis (D) is a cellular process, not a physical barrier.
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What is the main difference between the clonal selection theory proposed by MacFarlane Burnet and the selection theory proposed by Paul Ehrlich?
- A. Ehrlich proposed that structure complementarity between antigens and receptors is crucial for a specific response whereas Burnet overlooked the issue of specificity
- B. Ehrlich proposed that each cell able to produce antibodies would express several receptors, each specific for different antigens whereas Burnet proposed that each single antibody-producing cell expresses only one type of receptors
- C. Ehrlich thought that antibodies released from a cell were different from the receptors expressed on the same cell. Burnet thought that soluble antibodies and receptors produced by a single cell were identical
- D. Ehrlich's theory lacks the concept of release of a soluble form of the antigen receptor, an idea elaborated for the first time by Burnet.
Correct Answer: B
Rationale: The correct answer is B because Ehrlich proposed that each cell producing antibodies would express several receptors, each specific for different antigens, whereas Burnet proposed that each single antibody-producing cell expresses only one type of receptor. This is the main difference between the two theories. Ehrlich's concept of multiple receptors per cell allows for a broader range of specificity and diversity in the immune response. The other choices are incorrect because they do not directly address the main difference between the two theories as outlined above. Choice A is incorrect because both Ehrlich and Burnet emphasized the importance of specificity, but they differed in their views on receptor diversity per cell. Choice C is incorrect because it focuses on the identity of soluble antibodies and receptors, which is not the main differentiator between the two theories. Choice D is incorrect as it mentions the release of soluble antigen receptors, which is not the main point of differentiation between Ehrlich and Burnet's theories.
What groups listed below have true cell walls?
- A. algae
- B. mycoplasmas
- C. Gram-positive bacteria
- D. fungi
Correct Answer: B
Rationale: The correct answer is B: mycoplasmas. Mycoplasmas have cell walls, which contain peptidoglycan, making them structurally similar to typical bacteria. Algae (choice A) have cell walls made of cellulose, Gram-positive bacteria (choice C) have cell walls containing thick layers of peptidoglycan, and fungi (choice D) have cell walls made of chitin. Mycoplasmas lack a cell wall, but they have a flexible cell membrane that provides them with shape and protection.
What receptor is targeted in Grave's disease, a Type V hypersensitivity reaction?
- A. Insulin receptor
- B. Thyroid-stimulating hormone (TSH) receptor
- C. Complement receptor
- D. CD4 receptor
Correct Answer: B
Rationale: The correct answer is B: Thyroid-stimulating hormone (TSH) receptor. In Grave's disease, autoantibodies bind to and activate the TSH receptor on thyroid cells, leading to hyperthyroidism. This is a Type II hypersensitivity reaction. Insulin receptor (A) is not involved in Grave's disease. Complement receptor (C) is not the target in this condition. CD4 receptor (D) is primarily involved in T cell activation, not in Grave's disease.
Which cells are involved in innate immunity?
- A. B lymphocytes
- B. T lymphocytes
- C. Natural killer cells
- D. Plasma cells
Correct Answer: C
Rationale: The correct answer is C: Natural killer cells. Natural killer cells are part of the innate immune system and play a crucial role in identifying and destroying infected or abnormal cells. They are able to recognize and target cells that lack specific markers, providing a rapid response to infections.
Explanation for incorrect choices:
A: B lymphocytes are part of the adaptive immune system, not innate immunity.
B: T lymphocytes are also part of the adaptive immune system, not involved in innate immunity.
D: Plasma cells are differentiated B cells that produce antibodies in the adaptive immune response, not part of innate immunity.
The immunoglobulin Joining chain (J-chain) is
- A. only produced by T-Cells
- B. only produced by neutrophils
- C. associated with only multimeric forms of IgM and IgA
- D. associated with IgE for histamine release
Correct Answer: C
Rationale: Step-by-step rationale:
1. The J-chain is a polypeptide involved in the formation of polymeric IgM and IgA.
2. Polymeric forms of IgM and IgA contain the J-chain, aiding in their multimeric structure.
3. The J-chain is not exclusive to T-cells or neutrophils, making choices A and B incorrect.
4. IgE is associated with FcεRI receptors for histamine release, so choice D is incorrect.
Summary:
The correct answer is C because the J-chain is specifically associated with the multimeric forms of IgM and IgA, helping to form their structure. Choices A, B, and D are incorrect as the J-chain is not solely produced by T-cells, neutrophils, or associated with IgE for histamine release.