Nokea
Which of the following statements is most correct regarding Leishmania?
- A. Leishmaniasis is caused by an extracellular bacterium
- B. Leishmaniasis is associated with severe immunodeficiency
- C. An infected individual is less likely to suffer severe leishmaniasis if they make a TH2 rather than TH1 response to the pathogen
- D. Visceral leishmaniasis is the most severe form of leishmaniasis
Correct Answer: D
Rationale: The correct answer is D because visceral leishmaniasis is indeed the most severe form of leishmaniasis. Visceral leishmaniasis affects internal organs and can be fatal if left untreated.
A is incorrect because Leishmania is a protozoan parasite, not a bacterium. B is incorrect because leishmaniasis can affect individuals with normal immune systems, not just those with severe immunodeficiency. C is incorrect because a TH1 response is actually protective against severe leishmaniasis, not a TH2 response.
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The lectin and the classical pathway are similar because:
- A. The same component initiates the complement cascade
- B. The same enzyme cleaves C4 and C2
- C. They lead to the formation of the same C3 convertase
- D. They both involve recognition of an antigen/antibody complex as a trigger for complement activation
Correct Answer: C
Rationale: The lectin and classical pathways both lead to the formation of the same C3 convertase (C4b2a). This is because in the lectin pathway, mannose-binding lectin (MBL) binds to specific sugar residues on pathogens, activating MBL-associated serine proteases (MASPs) that cleave C4 and C2 to form the C3 convertase. Similarly, in the classical pathway, C1 complex binds to antigen-antibody complexes, activating C1s to cleave C4 and C2 to form the C3 convertase. This convergent step in both pathways results in the cleavage of C3 into C3a and C3b, leading to downstream complement activation. The other choices are incorrect because they do not accurately reflect the key similarity between the lectin and classical pathways in terms of the formation of the C3 convertase.
The human retina contains rods and cone which are able to
- A. convert the photo power to the chemical power
- B. absorption of ultraviolet
- C. convert photo power to electrical form and send action potentials to the brain
- D. absorption of infrared
Correct Answer: C
Rationale: The correct answer is C because rods and cones in the human retina convert light energy into electrical signals through phototransduction, which are then sent as action potentials to the brain via the optic nerve. This process allows for visual information to be transmitted and processed by the brain. Choice A is incorrect as it refers to the conversion of light energy to chemical energy, which is not the primary function of rods and cones. Choice B is incorrect as rods and cones do not specifically absorb ultraviolet light. Choice D is incorrect as rods and cones do not absorb infrared light.
Which is not a PAMP?
- A. Viral dsRNA
- B. Peptidoglycan
- C. ROS
- D. Flagellin
Correct Answer: C
Rationale: The correct answer is C: ROS (Reactive Oxygen Species) is not a PAMP (Pathogen-Associated Molecular Pattern) because it is not a specific molecular pattern derived from pathogens. PAMPs are recognized by the innate immune system to trigger an immune response. Viral dsRNA, peptidoglycan, and flagellin are all examples of PAMPs as they are specific molecules commonly found in pathogens that can be recognized by pattern recognition receptors (PRRs) on immune cells, leading to activation of the immune response.ROS, on the other hand, are reactive molecules produced by host cells in response to pathogens but are not specific molecular patterns derived from pathogens. Therefore, ROS is not considered a PAMP.
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.
Recognize the following that would be classified as a delayed hypersensitivity reaction.
- A. Anaphylaxis
- B. Allergic contact dermatitis
- C. Cytotoxic hypersensitivity
- D. Immune complex hypersensitivity
Correct Answer: B
Rationale: The correct answer is B: Allergic contact dermatitis. This is classified as a delayed hypersensitivity reaction because it involves activation of T cells, which takes time to develop. Anaphylaxis (A) is an immediate hypersensitivity reaction mediated by IgE. Cytotoxic hypersensitivity (C) involves antibodies attacking cells directly, not delayed. Immune complex hypersensitivity (D) involves immune complexes depositing in tissues, triggering inflammation, not T cell activation.