Nokea
What is not true about Salmonella thyphimurium?
- A. It is the causal agent of "hamburger disease"
- B. It is the second most common cause of food poisoning
- C. It is able to induce its own uptake by manipulating the actin cytoskeleton of host cells
- D. It is able to survive inside the phagosomes by manipulating the host actin cytoskeleton
Correct Answer: A
Rationale: The correct answer is A: It is the causal agent of "hamburger disease." Salmonella typhimurium is not the causal agent of "hamburger disease." Instead, Escherichia coli O157:H7 is the primary causal agent of this particular foodborne illness. Salmonella typhimurium is commonly associated with causing salmonellosis. Therefore, choice A is incorrect. Choices B, C, and D are all true statements about Salmonella typhimurium. It is the second most common cause of food poisoning, it is able to induce its own uptake by manipulating the actin cytoskeleton of host cells, and it is able to survive inside the phagosomes by manipulating the host actin cytoskeleton.
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Where and into what do activated B lymphocytes differentiate?
- A. Spleen; natural killer cells that destroy infected cells
- B. Bone marrow; plasma cells that secrete immunoglobulins
- C. Thymus; memory B-cells that retain a memory of the antigen
- D. Bursa of Fabricius; helper cells that in turn activate additional B lymphocytes
Correct Answer: B
Rationale: Activated B lymphocytes differentiate into plasma cells in the bone marrow, which produce and secrete antibodies.
Which of the following best illustrates selective genetic pressure in immune adaptation?
- A. Rroma populations and their genetic response to Yersinia pestis
- B. Mutation rates in viruses like the flu
- C. Increased pathogen diversity in unvaccinated populations
- D. Non-specific activation of innate immunity
Correct Answer: A
Rationale: Step 1: Selective genetic pressure refers to the process where specific genetic traits are favored due to environmental factors.
Step 2: Rroma populations and their genetic response to Yersinia pestis demonstrate selective genetic pressure as they have developed genetic adaptations to resist the plague bacterium.
Step 3: This adaptation is a result of prolonged exposure to the pathogen, leading to the survival and reproduction of individuals with genetic variations that confer resistance.
Step 4: Other choices are incorrect because mutation rates in viruses like the flu (B) do not necessarily involve genetic pressure, increased pathogen diversity in unvaccinated populations (C) is a consequence of lack of immunity, and non-specific activation of innate immunity (D) is not a selective process based on genetic traits.
A protein-protein interaction domain present both in TLR-4 and MyD88 is:
- A. CARD
- B. TIR
- C. Leucine rich repeat (LRR)
- D. Immunoglobulin-like domain
Correct Answer: B
Rationale: The correct answer is B: TIR. This is because both TLR-4 and MyD88 contain a Toll/interleukin-1 receptor (TIR) domain, which mediates protein-protein interactions in the Toll-like receptor signaling pathway. The other options, such as A (CARD), C (LRR), and D (Immunoglobulin-like domain), are not present in both TLR-4 and MyD88 and do not play a significant role in their interaction in the signaling pathway. This makes B the most appropriate choice as it accurately identifies the common protein-protein interaction domain between TLR-4 and MyD88.
Cancer cells go through stages of development. What accurately describes the stage of promotion (select all that apply)?
- A. Obesity is an example of a promoting factor
- B. The stage is characterized by increased growth rate and metastasis
- C. Withdrawal of promoting factors will reduce the risk of cancer development
- D. Tobacco smoke is a complete carcinogen that is capable of both initiation and promotion
Correct Answer: C
Rationale: Promotion involves enhancing the growth of initiated cells. Obesity and tobacco smoke are examples of promoting factors, and withdrawal of such factors can reduce cancer risk.
Which of the following statements about the functions of Ig is NOT correct
- A. IgM are the best at activating complement
- B. IgM bound to antigens are also the best at facilitating phagocytosis through the Fc receptor
- C. Antibodies can neutralize bacterial toxins
- D. Antibodies can inhibit binding of toxins to their receptors on host cells
Correct Answer: B
Rationale: The correct answer is B because IgG, not IgM, is the best at facilitating phagocytosis through the Fc receptor. IgM is the best at activating complement (A), antibodies can neutralize bacterial toxins (C), and antibodies can inhibit binding of toxins to their receptors on host cells (D). IgM primarily activates complement, while IgG is more efficient at facilitating phagocytosis through the Fc receptor. This distinction is crucial in understanding the functions of different immunoglobulins.