Nokea
Which molecule released by NK cells is responsible for inducing apoptosis?
- A. Perforin
- B. Granzyme
- C. Cytokines
- D. Antibodies
Correct Answer: B
Rationale: The correct answer is B: Granzyme. Granzyme is the molecule released by NK cells that induces apoptosis in target cells. It enters the target cell through perforin, which creates pores in the target cell membrane. Cytokines are signaling molecules released by various immune cells but do not directly induce apoptosis. Antibodies are produced by B cells and do not induce apoptosis. Perforin aids in the delivery of granzyme but is not responsible for inducing apoptosis itself. Therefore, Granzyme is the correct choice for inducing apoptosis by NK cells.
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In which of the following locations can IgA be found?
- A. In the intestinal lumen
- B. In the lamina propria
- C. In vesicles of enterocytes
- D. In all of the above
Correct Answer: D
Rationale: IgA can be found in the intestinal lumen, lamina propria, and vesicles of enterocytes. IgA is produced by plasma cells in the lamina propria and transported across the epithelial cells into the intestinal lumen where it provides mucosal immunity. It can also be found in vesicles of enterocytes before secretion. Therefore, the correct answer is D as IgA is present in all of the mentioned locations. Choices A, B, and C are incorrect individually as they only represent specific locations where IgA can be found, not all the locations where IgA is present in the gastrointestinal tract.
AIRE is expressed in
- A. Bone marrow
- B. Thymic cortical region
- C. Thymic medullary region
- D. LN cortex
Correct Answer: C
Rationale: The correct answer is C: Thymic medullary region. AIRE (Autoimmune Regulator) is expressed in the thymic medullary region. This region is crucial for central tolerance by deleting self-reactive T cells to prevent autoimmune reactions. AIRE regulates the expression of tissue-specific antigens in medullary thymic epithelial cells, leading to negative selection of autoreactive T cells. Choices A, B, and D are incorrect as AIRE is not primarily expressed in bone marrow, thymic cortical region, or LN cortex.
Which definition is the best description of the term genotype?
- A. Basic unit of heredity; arranged on chromosome
- B. Transmission of a disease from parent to child
- C. Genetic identity of an individual not seen as outward characteristics
- D. Family tree containing genetic characteristics and disorders of that family
Correct Answer: C
Rationale: Genotype refers to the genetic makeup of an organism, which may or may not be visible through phenotypic traits.
Which of the following sentences is NOT true about type I hypersensitivity reactions?
- A. Symptoms manifest in allergic individuals only after a second encounter with an allergen
- B. Food allergies can result in systemic anaphylaxis
- C. TH2 lymphocytes are involved in their development
- D. They can be classified as genetic disorders because they are caused by a single gene defect
Correct Answer: D
Rationale: Step 1: Type I hypersensitivity reactions are immediate allergic reactions that occur upon initial exposure to an allergen, not just after a second encounter.
Step 2: Food allergies can lead to systemic anaphylaxis due to the rapid release of mediators like histamine.
Step 3: TH2 lymphocytes play a crucial role in the development of type I hypersensitivity reactions by promoting IgE production.
Step 4: Type I hypersensitivity reactions are not generally classified as genetic disorders since they result from an immune response to allergens, not a single gene defect.
What is NOT true about innate immunity?
- A. Innate cells are immediately active, do not need clonal amplification or differentiation
- B. Innate cells can respond better and faster at a second encounter with the same pathogen
- C. Innate receptors recognizing pathogens do not have a fine specificity but rather recognize structures broadly found in different microbes
- D. Innate receptors can also recognize modified-self
Correct Answer: B
Rationale: The correct answer is B because innate immune cells do not respond better and faster at a second encounter with the same pathogen. This is a characteristic of adaptive immunity, not innate immunity. During a second encounter, adaptive immune cells produce a faster and stronger response due to memory cells formed during the initial exposure. In contrast, innate immune cells do not have memory cells and their response remains the same upon repeated encounters. Choice A is correct as innate cells are immediately active and do not require clonal amplification or differentiation. Choice C is correct as innate receptors recognize broad structures on pathogens. Choice D is correct as innate receptors can recognize modified-self, such as in autoimmune diseases.