Select the correct number of statements that are true.
- A. Only 1 and 3 are correct.
- B. Only 2 and 4 are correct.
- C. Only 3 and 4 are correct.
- D. All of the above are correct.
Correct Answer: A
Rationale: The correct answer is A. Statement 1 and 3 are true because selecting them would result in a correct answer. Statement 2 is incorrect as it claims that only 2 and 4 are correct, which contradicts the correct answer. Statement 4 is also incorrect as it claims that only 3 and 4 are correct, which is not consistent with the correct answer. The option "All of the above are correct" (D) is false because it includes statement 2, which is incorrect. Therefore, A is the correct choice because it accurately identifies the true statements.
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Which scientist is credited with identifying Toll-like receptors (TLRs) in innate immunity?
- A. Paul Ehrlich
- B. Jules Hoffman
- C. Edward Jenner
- D. Louis Pasteur
Correct Answer: B
Rationale: The correct answer is B: Jules Hoffman. He is credited with identifying Toll-like receptors (TLRs) in innate immunity. Hoffman's research provided crucial insights into how the immune system recognizes pathogens and triggers immune responses. Paul Ehrlich is known for his work on antibodies, Edward Jenner for developing the smallpox vaccine, and Louis Pasteur for his contributions to germ theory and vaccination. However, none of them are specifically associated with the discovery of Toll-like receptors in innate immunity.
Which condition is associated with increased susceptibility to bacterial infections due to complement deficiencies?
- A. Asthma
- B. Systemic lupus erythematosus (SLE)
- C. Streptococcus pneumoniae infections
- D. Chronic hepatitis
Correct Answer: C
Rationale: The correct answer is C: Streptococcus pneumoniae infections. Complement deficiencies impair the body's ability to fight bacterial infections, particularly encapsulated bacteria like Streptococcus pneumoniae. Asthma (A), SLE (B), and chronic hepatitis (D) are not directly associated with increased susceptibility to bacterial infections due to complement deficiencies. Asthma is a chronic respiratory condition, SLE is an autoimmune disease, and chronic hepatitis affects the liver. Therefore, only Streptococcus pneumoniae infections are directly linked to complement deficiencies.
Which antibody isotype is involved in allergic reactions?
- A. IgG
- B. IgM
- C. IgA
- D. IgE
Correct Answer: D
Rationale: The correct answer is D: IgE. IgE is the antibody isotype involved in allergic reactions. It binds to allergens and triggers the release of histamine and other chemicals, leading to allergic symptoms. IgG (choice A) is involved in long-term immunity, IgM (choice B) is the first antibody produced in response to an infection, and IgA (choice C) is mainly found in mucosal areas and helps prevent pathogens from entering the body. IgE is specifically associated with allergic responses due to its role in triggering the release of inflammatory mediators in response to allergens.
The human immunodeficiency virus (HIV)
- A. Is a retrovirus
- B. Is an RNA virus
- C. Is a lentivirus
- D. All of the above A, B and C
Correct Answer: D
Rationale: Step 1: HIV is a retrovirus because it contains RNA as its genetic material and uses the enzyme reverse transcriptase to convert its RNA into DNA.
Step 2: HIV is an RNA virus because its genetic material is RNA.
Step 3: HIV is a lentivirus which is a subgroup of retroviruses known for causing slow-progressing diseases.
Therefore, the correct answer is D as all statements A, B, and C are true based on the characteristics of HIV.
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.