Nokea
Which of the following is the best match between antibody class and major antibody effector function?
- A. IgG: Opsonization
- B. IgA: Complement activation
- C. IgE: Antibody-dependent cell-mediated cytotoxicity
- D. IgM: Neonatal immunity
Correct Answer: A
Rationale: The correct answer is A: IgG: Opsonization. IgG antibodies are known for their role in opsonization, where they tag pathogens for phagocytosis by immune cells. This process enhances the removal of pathogens. IgA is mainly involved in mucosal immunity and not complement activation, making choice B incorrect. IgE is associated with allergic reactions and not antibody-dependent cell-mediated cytotoxicity as stated in choice C. IgM is the first antibody produced in response to an infection and plays a role in neonatal immunity, making choice D incorrect.
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Which of the following DNA polymerases cleaves a DNA sequence at the direction of 5' → 3'?
- A. DNA polymerase I
- B. DNA polymerase II
- C. DNA polymerase III
- D. DNA polymerase IV
Correct Answer: A
Rationale: The correct answer is A: DNA polymerase I. DNA polymerase I has both 5' to 3' polymerase activity and 5' to 3' exonuclease activity, allowing it to cleave DNA in the 5' to 3' direction. This enzyme can remove RNA primers during DNA replication by cleaving them in the 5' to 3' direction and replace them with DNA nucleotides. DNA polymerase II, III, and IV do not have the same exonuclease activity as DNA polymerase I, so they are not capable of cleaving DNA sequences in the 5' to 3' direction like DNA polymerase I.
In LN naïve T cells and activated dendritic cells interact in the
- A. Subcapsular sinus
- B. Cortex
- C. Paracortex
- D. Medulla
Correct Answer: C
Rationale: The correct answer is C: Paracortex. Naïve T cells circulate through the blood and lymphatic system until they encounter antigens presented by activated dendritic cells in the paracortex of lymph nodes. The paracortex is the region where T cell activation and proliferation occur, leading to an immune response. The subcapsular sinus (A) is primarily involved in filtering lymph fluid, the cortex (B) contains B cell follicles, and the medulla (D) contains plasma cells and macrophages. Thus, the paracortex is the specific site of interaction between naïve T cells and activated dendritic cells in lymph nodes.
Tolerogenic dendritic cells
- A. Induce T cell unresponsiveness
- B. Do not secrete IL-12
- C. Express high levels of co-stimulatory molecules
- D. Have recognized PAMPs
Correct Answer: E
Rationale: I apologize, but it seems like there was a mistake in the question. The correct answer is not provided as choice "E." Could you please provide the correct choices for the question so I can provide you with the detailed explanation you are looking for?
Lymph consists of fluid that:
- A. Is taken up from tissues by lymphatic capillaries
- B. Carries antigens and mature dendritic cells to lymph nodes
- C. Is secreted by lymphocytes
- D. Two of these options are correct
Correct Answer: D
Rationale: Rationale:
1. A is correct as lymph is taken up from tissues by lymphatic capillaries.
2. B is correct as lymph carries antigens and mature dendritic cells to lymph nodes.
3. C is incorrect as lymph is not secreted by lymphocytes.
4. Therefore, D is correct as both A and B accurately describe the components and functions of lymph.
T-cell antigen receptors are distinguished from antibodies by which of the following
- A. T-Cell receptors are glycosylated
- B. T-cell receptors must interact with antigen uniquely presented by other cells but not with free antigen
- C. T-Cell receptors bind various cytokines
- D. T-Cell receptors bind complement to lyse cells
Correct Answer: B
Rationale: The correct answer is B. T-cell receptors must interact with antigens uniquely presented by other cells but not with free antigen. This is because T-cell receptors recognize antigens that are processed and presented on the surface of other cells via major histocompatibility complex (MHC) molecules. T-cell receptors specifically bind to the antigen-MHC complex, allowing T-cells to respond to specific foreign antigens.
A: T-cell receptors are not distinguished from antibodies by glycosylation. Both T-cell receptors and antibodies can be glycosylated, so this does not differentiate them.
C: T-cell receptors do not bind various cytokines. Cytokine receptors are separate entities that mediate cellular responses to cytokines.
D: T-cell receptors do not bind complement to lyse cells. Complement activation is a separate immune response mechanism not involving T-cell receptors.