Nokea
An example of a recombinant vaccine is
- A. DPT (Diphteria/Pertussis/Tetanus)
- B. Hepatitis B
- C. BCG
- D. Measles
Correct Answer: B
Rationale: The correct answer is B: Hepatitis B. Recombinant vaccines are made by inserting genetic material from a pathogen into another organism to stimulate an immune response. Hepatitis B vaccine is produced using recombinant DNA technology to create a non-infectious protein that triggers an immune response against the hepatitis B virus. DPT, BCG, and Measles vaccines are not examples of recombinant vaccines as they are made using different methods without genetic engineering.
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Which characteristics are seen with acute transplant rejection (select all that apply)?
- A. Treatment is supportive
- B. Only occurs with transplanted kidneys
- C. Organ must be removed when it occurs
- D. The recipient’s T cytotoxic lymphocytes attack the foreign organ
Correct Answer: D
Rationale: Acute transplant rejection involves the recipient's T cytotoxic lymphocytes attacking the transplanted organ, requiring immunosuppressive therapy.
What are the effects of histamine released from mast cells?
- A. Increased vascular permeability and bronchoconstriction
- B. Neutralization of antigens and opsonization
- C. Complement activation and T cell proliferation
- D. Direct lysis of pathogens
Correct Answer: A
Rationale: The correct answer is A because histamine released from mast cells causes increased vascular permeability, leading to edema, and bronchoconstriction, contributing to respiratory symptoms. This is a key mechanism in allergic reactions.
B: Neutralization of antigens and opsonization are functions of antibodies, not histamine.
C: Complement activation and T cell proliferation are separate immune responses not mediated by histamine.
D: Direct lysis of pathogens is typically carried out by immune cells like macrophages and natural killer cells, not histamine.
Choose the correct sequence in an allergic reaction.
- A. Allergen → mast cells → histamine → B cells → IgE antibodies
- B. Allergen → IgE antibodies → B cells → histamine → mast cells
- C. Allergen → B cells → IgE antibodies → mast cells → histamine
- D. Allergen → histamine → mast cells → IgE antibodies → B cells
Correct Answer: C
Rationale: Rationale for Answer C:
1. Allergen exposure triggers B cells to produce IgE antibodies specific to the allergen.
2. IgE antibodies bind to mast cells sensitizing them.
3. Upon re-exposure to allergen, allergen binds to IgE on mast cells.
4. This triggers release of histamine and other chemicals causing allergic symptoms.
Summary:
- Choice A: Incorrect because B cells do not produce IgE antibodies before allergen exposure.
- Choice B: Incorrect because IgE antibodies are produced by B cells, not the other way around.
- Choice D: Incorrect because histamine is released after allergen binds to IgE on sensitized mast cells.
The bacterial cytoplasmic membrane contains:
- A. ester-linked phospholipids, but no sterols
- B. ester-linked phospholipids and sterols
- C. ether-linked phospholipids, but no sterols
- D. ether-linked phospholipids, sulfolipids, and glycolipids
Correct Answer: A
Rationale: The correct answer is A because bacterial cytoplasmic membranes typically contain ester-linked phospholipids but no sterols. Ester-linked phospholipids are the main component of bacterial cell membranes, providing structure and function. Sterols, like cholesterol, are not commonly found in bacterial membranes. Choice B is incorrect because sterols are not present in bacterial membranes. Choice C is incorrect because ether-linked phospholipids are more commonly found in archaea, not bacteria. Choice D is incorrect because sulfolipids and glycolipids are not primary components of bacterial cytoplasmic membranes.
Where do T cells mature?
- A. Bone marrow
- B. Thymus
- C. Spleen
- D. Lymph nodes
Correct Answer: B
Rationale: The correct answer is B: Thymus. T cells mature in the thymus, where they undergo selection and maturation processes essential for their function in the immune system. The thymus provides a specialized environment for T cell development, including positive and negative selection to ensure self-tolerance and functional T cell repertoire.
A: Bone marrow is incorrect because it is the site of B cell maturation, not T cells.
C: Spleen is incorrect as it acts as a secondary lymphoid organ for immune response but not the site of T cell maturation.
D: Lymph nodes are incorrect as they are important for immune surveillance and activation but not the primary site for T cell maturation.