Nokea
Monoclonal antibodies can be used to:
- A. Block the proliferation of cancer cells
- B. Target cancer cells for destruction
- C. Inhibit inflammatory immune responses
- D. All of the above
Correct Answer: D
Rationale: The correct answer is D because monoclonal antibodies have the ability to block the proliferation of cancer cells by targeting specific antigens on the cancer cells. They can also target cancer cells for destruction through various mechanisms such as antibody-dependent cell-mediated cytotoxicity. Additionally, monoclonal antibodies can inhibit inflammatory immune responses by neutralizing pro-inflammatory mediators or blocking immune cell activation pathways. Therefore, all the options A, B, and C are correct, making D the correct answer.
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The rearrangement of gene segments that occurs randomly in B cell receptor genes and T cell receptor genes:
- A. Occurs during clonal expansion of B cells and T cells
- B. Involves rapid genetic mutation after lymphocytes become activated
- C. Allows the mature lymphocyte population to recognize an enormous diversity of antigens
- D. Occurs in the DNA of all cells in the body
Correct Answer: C
Rationale: Step 1: Gene rearrangement in B cell and T cell receptor genes creates unique receptor proteins.
Step 2: This diversity allows mature lymphocytes to recognize a wide range of antigens.
Step 3: This process is crucial for adaptive immune response and antigen specificity.
Step 4: Choices A and B do not accurately describe gene rearrangement.
Step 5: Choice D is incorrect as gene rearrangement is specific to lymphocytes, not all cells in the body.
An essential cofactor for restriction endonuclease enzyme activity is
- A. Zn2+
- B. Mg2+
- C. Co2+
- D. Ca2+
Correct Answer: B
Rationale: The correct answer is B: Mg2+. Mg2+ is an essential cofactor for restriction endonuclease enzymes because it stabilizes the enzyme-substrate complex, promotes proper binding of the enzyme to DNA, and facilitates the catalytic activity of the enzyme. Mg2+ ions help in the coordination of the active site residues and the phosphate backbone of DNA, which is crucial for the cleavage of DNA strands. Zn2+, Co2+, and Ca2+ do not provide the necessary coordination and stabilization required for restriction endonuclease enzyme activity, making them incorrect choices.
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 cellular structure is involved in digesting engulfed pathogens during phagocytosis?
- A. Lyosomes
- B. Golgi apparatus
- C. Endoplasmic reticulum
- D. Mitochondria
Correct Answer: A
Rationale: The correct answer is A: Lysosomes. Lysosomes contain enzymes that break down engulfed pathogens during phagocytosis. First, the pathogen is engulfed by the cell membrane forming a phagosome. Next, the phagosome fuses with a lysosome forming a phagolysosome where digestion occurs. Golgi apparatus (B) is involved in protein processing and packaging. Endoplasmic reticulum (C) is responsible for protein synthesis and lipid metabolism. Mitochondria (D) produce energy in the form of ATP.
What lineage do natural killer (NK) cells belong to?
- A. Myeloid lineage
- B. Erythroid lineage
- C. Lymphoid lineage
- D. Granulocyte lineage
Correct Answer: C
Rationale: The correct answer is C: Lymphoid lineage. NK cells are a type of lymphocyte that is part of the innate immune system. They are derived from common lymphoid progenitors in the bone marrow. NK cells play a crucial role in recognizing and killing infected or abnormal cells. Myeloid lineage (A) gives rise to cells like macrophages and granulocytes, not NK cells. Erythroid lineage (B) produces red blood cells, and granulocyte lineage (D) gives rise to neutrophils, basophils, and eosinophils, not NK cells. Therefore, the correct choice is C as NK cells originate from the lymphoid lineage.