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What are the most common immunosuppressive agents used to prevent rejection of transplanted organs?
- A. Cyclosporine, sirolimus, and muromonab-CD3
- B. Prednisone, polyclonal antibodies, and cyclosporine
- C. Azathioprine, mycophenolate mofetil, and sirolimus
- D. Tacrolimus, prednisone, and mycophenolate mofetil
Correct Answer: D
Rationale: Tacrolimus, prednisone, and mycophenolate mofetil are commonly used to prevent organ rejection.
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The joints most commonly involved with rheumatoid arthritis include:
- A. Symmetrical involvement of major joints.
- B. Small joints of hands and feet.
- C. Spine,from the sacrum upward to cervical.
- D. Slightly movable joints of the axial skeleton.
Correct Answer: B
Rationale: Rheumatoid arthritis primarily affects small joints symmetrically, especially those in the hands and feet. Major joints and axial skeleton involvement occurs but is less characteristic of early disease presentation.
How do NK cells kill target cells?
- A. By producing antibodies
- B. Through secretion of cytokines
- C. By releasing perforin and granzyme
- D. By phagocytosis
Correct Answer: C
Rationale: The correct answer is C. NK cells kill target cells by releasing perforin and granzyme. Perforin creates pores in the target cell's membrane, allowing granzyme to enter and induce apoptosis. Antibodies (choice A) are produced by B cells, not NK cells. Cytokines (choice B) regulate immune responses but do not directly kill cells. Phagocytosis (choice D) involves engulfing and digesting pathogens, which is not how NK cells kill target cells.
Which of the following is a molecule that inhibits T cell activation, is highly expressed in Tregs and is used in a recombinant (synthetic) form to treat some autoimmune diseases?
- A. CD86
- B. CTLA-4
- C. MHC class II
- D. CD4
Correct Answer: B
Rationale: The correct answer is B: CTLA-4. CTLA-4 inhibits T cell activation by binding to CD80/CD86 on antigen-presenting cells, preventing the co-stimulatory signal required for T cell activation. It is highly expressed in Tregs, which suppress immune responses. Recombinant CTLA-4 (e.g., abatacept) is used to treat autoimmune diseases by blocking T cell activation.
Explanation for other choices:
A: CD86 is a co-stimulatory molecule that activates T cells, not inhibits them.
C: MHC class II molecules present antigens to T cells, they do not inhibit T cell activation.
D: CD4 is a co-receptor that helps T cells recognize antigens presented by MHC class II molecules, it does not inhibit T cell activation.
Which condition is an example of Type IV hypersensitivity?
- A. Multiple sclerosis
- B. Grave's disease
- C. Anaphylaxis
- D. Eczema
Correct Answer: A
Rationale: The correct answer is A: Multiple sclerosis. Type IV hypersensitivity involves T cell-mediated immune reactions, leading to tissue damage. In multiple sclerosis, myelin sheath destruction is caused by activated T cells attacking self-antigens.
Incorrect choices:
B: Grave's disease is an example of Type II hypersensitivity involving autoantibodies targeting specific cells.
C: Anaphylaxis is a Type I hypersensitivity reaction mediated by IgE antibodies causing rapid and severe allergic reactions.
D: Eczema is a chronic inflammatory skin condition involving complex immune mechanisms not specific to Type IV hypersensitivity.
Where and into what do activated B lymphocytes differentiate?
- A. Spleen; natural killer cells that destroy infected cells
- B. Bone marrow; plasma cells that secrete immunoglobulins
- C. Thymus; memory B-cells that retain a memory of the antigen
- D. Bursa of Fabricius; helper cells that in turn activate additional B lymphocytes
Correct Answer: B
Rationale: Activated B lymphocytes differentiate into plasma cells in the bone marrow, which produce and secrete antibodies.