Nokea
Which of the following immunoglobulins is present normally in plasma at the highest concentration?
- A. IgG
- B. IgM
- C. IgA
- D. IgD
Correct Answer: A
Rationale: The correct answer is A: IgG. IgG is the most abundant immunoglobulin in plasma, comprising around 75% of total immunoglobulins. It is produced in response to infections and provides long-term immunity. IgM is the first antibody produced in response to an infection, but its concentration decreases over time. IgA is mainly found in mucosal areas and secretions. IgD is present in small amounts and its function is not fully understood. Thus, IgG is the correct answer due to its high concentration in plasma and important role in long-term immunity.
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Identify the mismatched receptor: ligand pair
- A. NOD2: peptidoglycan
- B. TLR9: CpG DNA
- C. TLR5: dsRNA
- D. RIG-I: viral RNA
Correct Answer: C
Rationale: TLR5 recognizes flagellin, not dsRNA. This is why choice C is the correct answer. NOD2 binds to peptidoglycan (A), TLR9 binds to CpG DNA (B), and RIG-I recognizes viral RNA (D). Each receptor has specificity for a different ligand, making choice C the mismatched pair.
Neurons are
- A. Cells specialized for carrying signals
- B. The functional units of the nervous system
- C. consists of A cell body, Dendrites and Axons
- D. all above
Correct Answer: D
Rationale: The correct answer is D because neurons are specialized cells that carry signals, making them the functional units of the nervous system. Neurons consist of a cell body, dendrites, and axons, fulfilling the criteria mentioned in options A, B, and C. Therefore, option D encompasses all the essential characteristics of neurons, making it the correct choice. Options A, B, and C individually do not fully capture the comprehensive nature of neurons, as they only cover specific aspects of what neurons are, whereas option D encompasses all the correct statements regarding neurons.
Afferent lymphatic vessels do not
- A. Transport antigens from tissues to LN
- B. Enter LN at more than one site
- C. Transport antigens from blood to LN
- D. Connect tissues to secondary lymphoid organs
Correct Answer: C
Rationale: Rationale: Afferent lymphatic vessels transport lymph containing antigens from tissues to lymph nodes (LN). Option C is correct because afferent lymphatics do not transport antigens directly from the blood to LN. Other choices are incorrect because afferent lymphatics enter LN at multiple sites (B), transport antigens from tissues to LN (A), and connect tissues to secondary lymphoid organs (D).
What is a hallmark of Type IV hypersensitivity?
- A. It is immediate and IgE-mediated
- B. It is delayed and T cell-mediated
- C. It involves immune complexes
- D. It stimulates mast cells to release histamine
Correct Answer: B
Rationale: The correct answer is B because Type IV hypersensitivity reactions are delayed and T cell-mediated. Upon exposure to an antigen, sensitized T cells, specifically CD4+ T cells, release cytokines that recruit and activate macrophages and other effector cells, leading to tissue damage. Choice A is incorrect because Type I hypersensitivity reactions are immediate and IgE-mediated. Choice C is incorrect because immune complex-mediated hypersensitivity reactions are typically associated with Type III hypersensitivity. Choice D is incorrect because histamine release by mast cells is characteristic of Type I hypersensitivity reactions, not Type IV.
Which of these are a type of mutation?
- A. base substitution
- B. translocation
- C. insertion sequences
- D. recombination
Correct Answer: D
Rationale: The correct answer is D: recombination. Recombination is a type of mutation that involves the exchange of genetic material between two DNA molecules. This process can lead to genetic variation and evolution. Base substitution (A) is a point mutation where one base is replaced by another. Translocation (B) involves the movement of a segment of DNA to another location in the genome. Insertion sequences (C) are short segments of DNA that can move within the genome but are not considered a type of mutation. Recombination (D) is the only choice directly related to a type of mutation involving the exchange of genetic material.