Nokea
Which of the following is considered a defining characteristic of a TH2 response?
- A. Production of IgM antibodies
- B. Activation of CTL
- C. Recruitment and activation of neutrophils
- D. Production of IgE antibodies
Correct Answer: D
Rationale: The correct answer is D: Production of IgE antibodies. A TH2 response is characterized by the production of IgE antibodies, which are essential in allergic reactions. IgM antibodies (A) are produced during the primary immune response. Activation of CTL (B) is associated with a TH1 response. Neutrophils (C) are primarily involved in the innate immune response and are not specific to TH2 responses. In summary, the production of IgE antibodies is a defining characteristic of a TH2 response, distinguishing it from other immune responses.
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Identify the correct statement(s). In eukaryotic microorganisms:
- A. mRNA is short-lived (minutes).
- B. a single, circular chromosome is present.
- C. 5s, 16s, and 23s ribosomal RNA's are present.
- D. extrachromosomal DNA can be present.
Correct Answer: D
Rationale: The correct answer is D because extrachromosomal DNA, such as plasmids, can be present in eukaryotic microorganisms. This is true for certain organisms like yeast and some fungi. These DNA molecules are separate from the main chromosomal DNA and can carry additional genetic information.
A: mRNA in eukaryotic microorganisms is not short-lived; it can have varying lifespans depending on the specific mRNA molecule and cellular conditions.
B: Eukaryotic microorganisms typically have multiple linear chromosomes, not a single circular chromosome.
C: While 5s, 16s, and 23s ribosomal RNAs are present in prokaryotic organisms, eukaryotic microorganisms have different types of ribosomal RNA subunits.
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.
A naïve lymphocyte:
- A. Does not yet express antigen receptors
- B. Is not yet considered mature
- C. Has not yet been activated by antigen
- D. Is found only in primary lymphoid tissues
Correct Answer: C
Rationale: Step-by-step rationale:
1. Naïve lymphocytes have antigen receptors but have not been activated by antigen.
2. Activation is necessary for their differentiation into effector cells.
3. Naïve lymphocytes are considered mature as they have completed development.
4. They circulate in secondary lymphoid tissues, not just primary lymphoid tissues.
Summary:
Choice C is correct because naïve lymphocytes have antigen receptors but have not been activated by antigen. Choices A, B, and D are incorrect because naïve lymphocytes do express antigen receptors, are considered mature, and can be found in both primary and secondary lymphoid tissues.
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.
Which of the following is a primary lymphoid organ?
- A. Spleen
- B. Thymus
- C. Lymph node
- D. Mucosal immune system
Correct Answer: B
Rationale: The correct answer is B: Thymus. The thymus is considered a primary lymphoid organ because it is where T lymphocytes (T cells) mature and differentiate. T cells play a crucial role in the adaptive immune response. The thymus is responsible for educating T cells to recognize self versus non-self antigens.
Summary:
A: Spleen is a secondary lymphoid organ involved in filtering blood and producing antibodies, not where T cells mature.
C: Lymph node is also a secondary lymphoid organ where immune cells interact but not where T cells mature.
D: Mucosal immune system refers to the immune system in mucosal tissues, not a specific primary lymphoid organ.