Nokea
What is a key difference between innate and adaptive immunity?
- A. Innate immunity develops memory
- B. Adaptive immunity is always functional
- C. Innate immunity is rapid and non-specific
- D. Adaptive immunity does not require activation
Correct Answer: C
Rationale: Correct Answer: C
Rationale:
1. Innate immunity is rapid: It provides immediate defense against pathogens.
2. Innate immunity is non-specific: It reacts in the same way to all pathogens.
3. Adaptive immunity, on the other hand, is slower and pathogen-specific.
4. Adaptive immunity develops memory to provide long-lasting protection.
Summary:
A: Innate immunity does not develop memory; adaptive immunity does.
B: Adaptive immunity may not always be functional due to various factors.
D: Adaptive immunity requires activation through exposure to specific antigens.
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How do cytokines typically function in the body?
- A. In an endocrine manner
- B. In an autocrine and paracrine manner
- C. Solely by direct contact with pathogens
- D. By degrading immune cells
Correct Answer: B
Rationale: The correct answer is B because cytokines primarily function in an autocrine and paracrine manner. Autocrine signaling occurs when a cell produces a cytokine that acts on the same cell, while paracrine signaling involves cytokines acting on nearby cells. This allows cytokines to regulate immune responses locally. Option A is incorrect as endocrine signaling involves hormones acting on distant target cells via the bloodstream, which is not the primary function of cytokines. Option C is incorrect because cytokines do not require direct contact with pathogens to function. Option D is incorrect as cytokines do not degrade immune cells but rather regulate immune responses.
What stimulates aldosterone secretion from the adrenal cortex?
- A. Excessive water intake
- B. Increased serum osmolality
- C. Decreased serum potassium
- D. Decreased sodium and water
Correct Answer: D
Rationale: Aldosterone secretion is stimulated by decreased sodium and water levels (renin-angiotensin-aldosterone system activation) and low blood pressure.
The differentiation of activated Th cells into various effector subsets depends mostly on:
- A. Signal 1 of activation
- B. The influence of polarizing cytokines secreted by dendritic cells
- C. Whether the T cell expresses CD4 or CD8
- D. The duration of signaling induced by TCR binding to peptide-MHC
Correct Answer: B
Rationale: The correct answer is B because polarizing cytokines secreted by dendritic cells play a crucial role in determining the differentiation of activated Th cells into specific effector subsets. These cytokines guide the Th cells towards different functional phenotypes, such as Th1, Th2, Th17, or Treg cells. This process helps tailor the immune response to the specific type of pathogen encountered. Choices A, C, and D are incorrect because while signal 1 of activation, T cell receptor co-receptors, and duration of signaling are important factors in T cell activation and differentiation, they do not have as direct and significant an impact on effector subset differentiation as the influence of polarizing cytokines.
Which of the following statements is incorrect?
- A. BLASTX searches protein databases
- B. BLASTX use translated nucleotide as the query sequence
- C. Both TBLASTX and TBLASTN translate query into 6 reading frames
- D. BLASTN searches protein databases
Correct Answer: D
Rationale: The correct answer is D because BLASTN searches nucleotide databases, not protein databases. BLASTN uses a nucleotide sequence as the query to find similar sequences in nucleotide databases. This is different from BLASTX, which searches protein databases using translated nucleotide sequences (answer A is correct). TBLASTX and TBLASTN translate the query sequence into six reading frames to search for similarities in both nucleotide and protein databases (answer C is correct). BLASTN is specifically designed for nucleotide sequence searches, making statement D incorrect.
What is the significance of isotype switching in B cells?
- A. It enables the production of IgM only
- B. It enhances antibody affinity for antigens
- C. It changes the constant region to produce different antibody isotypes
- D. It eliminates antigen-specific B cells
Correct Answer: C
Rationale: Isotype switching in B cells involves changing the constant region to produce different antibody isotypes, such as IgG, IgA, or IgE. This is important for diversifying the functions of antibodies without altering antigen specificity. It allows for different effector functions, such as opsonization, neutralization, or complement activation. This process does not eliminate antigen-specific B cells, as it maintains the immunological memory. Isotype switching does not directly affect antibody affinity for antigens, which is primarily determined by somatic hypermutation and affinity maturation. It is not limited to producing IgM only, as B cells can switch to other isotypes based on the cytokine microenvironment.