Nokea
The recirculation of naïve lymphocytes follows which sequential order?
- A. Blood, HEV, LN, efferent lymphatics, thoracic duct, blood
- B. Blood, afferent lymphatics, LN, thoracic duct, blood
- C. Inflammatory sites, afferent lymphatics, LN, efferent lymphatics, thoracic duct, blood
- D. Both A and C are correct
Correct Answer: A
Rationale: The correct answer is A because naïve lymphocytes circulate through blood, enter lymph nodes (LN) via high endothelial venules (HEV), encounter antigens in LN, exit via efferent lymphatics, drain into the thoracic duct, and return to blood circulation. Choice B is incorrect because it skips the step of entering LN through HEV. Choice C is incorrect because it starts with inflammatory sites instead of blood, and it also lacks the step of entering LN through HEV. Choice D is incorrect as only option A correctly follows the sequential order of recirculation of naïve lymphocytes.
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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.
What is the mechanism of tissue damage in Type II hypersensitivity?
- A. Immune complex deposition
- B. Antibody binding to cell surface antigens, triggering complement activation or phagocytosis
- C. Mast cell degranulation
- D. T cell-mediated cytotoxicity
Correct Answer: B
Rationale: The correct answer is B: Antibody binding to cell surface antigens, triggering complement activation or phagocytosis. In Type II hypersensitivity, antibodies bind to antigens on host cells, leading to complement activation or phagocytosis by immune cells. This results in cell damage or destruction. Immune complex deposition (A) is more characteristic of Type III hypersensitivity. Mast cell degranulation (C) is seen in Type I hypersensitivity. T cell-mediated cytotoxicity (D) is associated with Type IV hypersensitivity, not Type II. Therefore, choice B is the most accurate mechanism of tissue damage in Type II hypersensitivity.
What could happen to the woman’s serum osmolality as a result of this meal?
- A. Increased
- B. No change
- C. Decreased
- D. Unchanged
Correct Answer: B
Rationale: The meal contains high amounts of sodium from salt pork and gravy, which would increase serum osmolality due to increased sodium concentration in the blood.
A hybridoma:
- A. Secretes both polyclonal and monoclonal antibodies
- B. Is generated from the fusion of two antigen-activated B cells
- C. Can live in tissue culture indefinitely
- D. All of these options describe a hybridoma
Correct Answer: C
Rationale: Step-by-step rationale:
1. Hybridoma is a cell line formed by the fusion of a B cell (producing a specific antibody) and a myeloma cell.
2. Choice C is correct because hybridomas can be immortalized and cultured indefinitely.
3. Choice A is incorrect because hybridomas produce monoclonal antibodies, not polyclonal antibodies.
4. Choice B is incorrect because hybridomas are formed from a single B cell and a myeloma cell, not two antigen-activated B cells.
5. Choice D is incorrect as only option C accurately describes a hybridoma's characteristic of indefinite tissue culture survival.
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.