Immunopathology mcqs — Source Paper Awaiting Edit

Question 1

A male infant is born at term with no congenital anomalies noted. A year later he has failure to thrive and has had one bacterial pneumonia after another, with both Haemophilus influenzae and Streptococcus pneumoniae cultured from sputum. Which disease is he most likely to have?

Accepted Answer

X-linked agammaglobulinemia — Recurrent bacterial infections suggest impaired B-cell function with lack of immunoglobulin production. Once protective maternal antibodies wane, the disease manifests more severely. ---

Question 2

A 52-year-old man with chronic kidney disease receives a renal allograft matched by tissue typing for HLA-DR (Class II) antigens. He does not develop rejection; his serum creatinine remains normal. Which immunologic abnormality has most likely been avoided by the tissue typing?

Accepted Answer

CD4 lymphocyte activation — Class II HLA antigens are central to CD4 lymphocyte activation, which drives much of the alloimmune response against a transplanted organ. ---

Question 3

A hypersensitivity response is noted to be stimulated by release of IL-4 and IL-5, accompanied by eosinophilia. This response is most likely directed against which of the following?

Accepted Answer

Liver flukes — Tissue-invasive parasitic infestations can trigger an eosinophilic response driven by a TH2 immune reaction with IL-4 and IL-5. The parasite can also trigger an IgE response via Fc receptors on mast cells, eosinophils, and basophils, causing degranulation and cytokine release. ---

Question 4

A 28-year-old woman is given intravenous penicillin to treat infective endocarditis. Within minutes she develops severe difficulty breathing with respiratory stridor and tachypnea, and an erythematous rash over most of her body. Her symptoms are most likely produced by release of which chemical mediator?

Accepted Answer

Histamine — This is a type I hypersensitivity reaction with systemic anaphylaxis, mediated in part by histamine released from mast cells, causing increased vascular permeability. About 20% of people have some reaction to penicillin or similar drugs, and a minority of these are severe. ---

Question 5

A 28-year-old man suffers a bee sting, and his wife searches frantically for the medical kit with injectable epinephrine. Which immunologic mechanism are they trying to circumvent?

Accepted Answer

Release of preformed tryptase — Bee sting allergen exposure can cause systemic anaphylaxis (type I hypersensitivity), which can be life-threatening. Epinephrine counteracts mediators such as histamine released from mast cells; an H1 blocker (e.g., diphenhydramine) is also useful. Mast cells contain many compounds besides biogenic amines — serum tryptase rises on mast cell degranulation and can help confirm anaphylaxis when the history is unclear, and serves as a marker of mast cell burden and anaphylaxis risk. ---

Question 6

A 55-year-old woman has had increasing difficulty swallowing over the past year. On exam her blood pressure is 210/110 mm Hg. Testing shows a positive ANA with a nucleolar pattern on immunofluorescence; serum complement levels are normal. Which renal lesion is most likely to be seen on renal biopsy?

Accepted Answer

Hyperplastic arteriolosclerosis — These findings are typical of diffuse scleroderma. Hypertensive emergency (malignant hypertension, systolic ≥180 and/or diastolic ≥120 mmHg with acute or ongoing end-organ damage) can result in this characteristic vascular renal lesion. ---

Question 7

A positive tuberculin skin test, with a firm 15 mm diameter dark red area of induration on the forearm, appears 60 hours after injection of purified protein derivative (PPD). This finding is most likely a consequence of which type of hypersensitivity reaction?

Accepted Answer

Type IV hypersensitivity — The tuberculin skin test relies on an intact cell-mediated immune response. It is positive with prior mycobacterial exposure, so memory T cells are present and can be reactivated. ---

Question 8

A study of immunofluorescence patterns in skin biopsies is performed. One immunofluorescence pattern with antibody to IgG shows a band of immunofluorescence at the dermal-epidermal junction. This pattern is most likely based on which pathologic mechanism?

Accepted Answer

Trapping of antigen-antibody complexes — This banded pattern is typical of a type III hypersensitivity reaction, in which antigen-antibody complexes become trapped along basement membranes. --- Note: Question 37's stem an

Immunopathology mcqs — Source Paper Awaiting Edit

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