Immunopathology US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Immunopathology. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Immunopathology US Medical PG Question 1: A scientist in Chicago is studying a new blood test to detect Ab to EBV with increased sensitivity and specificity. So far, her best attempt at creating such an exam reached 82% sensitivity and 88% specificity. She is hoping to increase these numbers by at least 2 percent for each value. After several years of work, she believes that she has actually managed to reach a sensitivity and specificity much greater than what she had originally hoped for. She travels to China to begin testing her newest blood test. She finds 2,000 patients who are willing to participate in her study. Of the 2,000 patients, 1,200 of them are known to be infected with EBV. The scientist tests these 1,200 patients' blood and finds that only 120 of them tested negative with her new exam. Of the patients who are known to be EBV-free, only 20 of them tested positive. Given these results, which of the following correlates with the exam's specificity?
- A. 82%
- B. 90%
- C. 84%
- D. 86%
- E. 98% (Correct Answer)
Immunopathology Explanation: ***98%***
- **Specificity** measures the proportion of **true negatives** among all actual negatives.
- In this case, 800 patients are known to be EBV-free (actual negatives), and 20 of them tested positive (false positives). This means 800 - 20 = 780 tested negative (true negatives). Specificity = (780 / 800) * 100% = **98%**.
*82%*
- This value represents the *original sensitivity* before the scientist’s new attempts to improve the test.
- It does not reflect the *newly calculated specificity* based on the provided data.
*90%*
- This value represents the *newly calculated sensitivity* of the test, not the specificity.
- Out of 1200 EBV-infected patients, 120 tested negative (false negatives), meaning 1080 tested positive (true positives). Sensitivity = (1080 / 1200) * 100% = 90%.
*84%*
- This percentage is not directly derived from the information given for either sensitivity or specificity after the new test results.
- It does not correspond to any of the calculated values for the new test's performance.
*86%*
- This percentage is not directly derived from the information given for either sensitivity or specificity after the new test results.
- It does not correspond to any of the calculated values for the new test's performance.
Immunopathology US Medical PG Question 2: A 40-year-old man presents to a clinic in Michigan in December complaining of painful blue fingers and toes. He also complains of numbness and tingling. The patient’s vital signs are within normal limits, and his symptoms typically disappear when he comes back into a warm room. The patient also notes that he recently moved to the area from Arizona and had recently recovered from a viral infection in which he had a low-grade fever and severe lymphadenopathy. Which of the following tests would most likely be positive in this patient?
- A. Direct Coomb’s test with anti-C3 reagent (Correct Answer)
- B. Anti-centromere antibody
- C. Anti-Ro antibody
- D. Indirect Coomb’s test
- E. Direct Coomb’s test with anti-IgG reagent
Immunopathology Explanation: ***Direct Coombs test with anti-C3 reagent***
- The patient presents with classic symptoms of **cold agglutinin disease**, characterized by painful blue fingers and toes (acrocyanosis) triggered by cold exposure that resolves with warming.
- The recent **viral infection with severe lymphadenopathy** suggests infections such as **Mycoplasma pneumoniae, EBV, or CMV**, which are well-known triggers for cold agglutinin disease.
- Cold agglutinins are **IgM antibodies** that bind to red blood cells at cold temperatures, causing **complement activation** (C3d deposition) and **extravascular hemolysis**.
- The **direct Coombs test with anti-C3 reagent** detects complement (C3) bound to RBC surfaces and is the diagnostic test of choice for cold agglutinin disease.
- The recent move from Arizona to Michigan in December provides the cold exposure trigger needed to manifest symptoms.
*Direct Coombs test with anti-IgG reagent*
- This test detects **IgG antibodies bound to red blood cells** and is positive in **warm autoimmune hemolytic anemia**, not cold agglutinin disease.
- Cold agglutinin disease is mediated by **IgM antibodies and complement (C3)**, not IgG, so this test would be negative.
*Indirect Coombs test*
- The **indirect Coombs test** detects **free antibodies in serum** against RBCs and is used primarily for blood typing and cross-matching.
- While it may detect cold agglutinins in serum, the **direct Coombs with anti-C3** is the more specific and diagnostic test for cold agglutinin disease.
*Anti-centromere antibody*
- **Anti-centromere antibodies** are highly specific for **limited cutaneous systemic sclerosis (CREST syndrome)**, which can present with Raynaud's phenomenon.
- However, the **acute onset** following a viral illness, the **severe lymphadenopathy**, and the **cold-triggered acrocyanosis** are more consistent with cold agglutinin disease rather than a chronic autoimmune connective tissue disease.
- Systemic sclerosis typically has a more insidious onset and is not triggered by viral infections.
*Anti-Ro antibody*
- **Anti-Ro antibodies** are associated with **Sjögren's syndrome** and **systemic lupus erythematosus (SLE)**.
- While Raynaud's can occur in these conditions, the clinical presentation with recent viral infection, severe lymphadenopathy, and cold-triggered symptoms points to cold agglutinin disease rather than SLE or Sjögren's syndrome.
Immunopathology US Medical PG Question 3: A researcher is studying the circulating factors that are released when immune cells are exposed to antigens. Specifically, she is studying a population of CD2+ cells that have been activated acutely. In order to determine which factors are secreted by these cells, she cultures the cells in media and collects the used media from these plates after several days. She then purifies a small factor from this media and uses it to stimulate various immune cell types. She finds that this factor primarily seems to increase the growth and prolong the survival of other CD2+ cells. Which of the following is most likely the factor that was purified by this researcher?
- A. Interleukin-2 (Correct Answer)
- B. Interleukin-3
- C. Interleukin-4
- D. Interleukin-5
- E. Interleukin-1
Immunopathology Explanation: ***Interleukin-2***
- **Interleukin-2 (IL-2)** is a crucial cytokine for the **growth**, **proliferation**, and **survival** of T lymphocytes, which are CD2+ cells.
- Activated T cells, like the acute CD2+ cells in the scenario, are a primary source of IL-2, and IL-2 acts in an **autocrine** and **paracrine** fashion to stimulate other T cells.
*Interleukin-3*
- **Interleukin-3 (IL-3)** primarily stimulates the growth and differentiation of **hematopoietic stem cells** and progenitors, not specifically mature CD2+ cells.
- It plays a role in the development of various myeloid cell lineages and mast cells, and its main effect is not confined to T cells.
*Interleukin-4*
- **Interleukin-4 (IL-4)** is critical for the differentiation of naive T helper cells into **Th2 cells** and is a key cytokine for **B cell proliferation** and **antibody class switching** to IgE.
- While it has immunomodulatory effects on T cells, its primary role is not in promoting the generalized growth and survival of other CD2+ cells.
*Interleukin-5*
- **Interleukin-5 (IL-5)** is predominantly involved in the growth, differentiation, and activation of **eosinophils**.
- It also plays a role in B cell growth and IgA production, but its effects are not primarily on universal CD2+ cell growth and survival.
*Interleukin-1*
- **Interleukin-1 (IL-1)** is a **pro-inflammatory cytokine** produced by macrophages, monocytes, and other immune cells in response to infection or injury.
- It primarily mediates **acute phase responses**, fever, and activates endothelial cells, but its main function is not to promote the growth and survival of T lymphocytes.
Immunopathology US Medical PG Question 4: A 3-year-old boy presents to the pediatrics clinic for follow-up. He has a history of severe pyogenic infections since birth. Further workup revealed a condition caused by a defect in CD40 ligand expressed on helper T cells. This congenital immunodeficiency has resulted in an inability to class switch and a poor specific antibody response to immunizations. Which of the following best characterizes this patient's immunoglobulin profile?
- A. Increased IgM; decreased IgG, IgA, and IgE (Correct Answer)
- B. Increased IgE and IgA; and decreased IgM
- C. Increased IgE
- D. Decreased IgA
- E. Decreased Interferon gamma
Immunopathology Explanation: ***Increased IgM; decreased IgG, IgA, and IgE***
- The described condition is **Hyper-IgM Syndrome** due to a defect in **CD40 ligand**, which prevents B cells from class-switching.
- This results in the continued production of **IgM** (which does not require CD40L for its synthesis) and *decreased levels of all other immunoglobulin isotypes* (IgG, IgA, IgE).
*Increased IgE and IgA; and decreased IgM*
- This profile is not characteristic of Hyper-IgM syndrome; it might be seen in other immunodeficiencies but not one caused by a CD40L defect.
- A decrease in IgM production would indicate a defect in early B-cell development or IgM synthesis, which is contrary to the features of Hyper-IgM syndrome where IgM is typically high.
*Increased IgE*
- While increased IgE can be a feature of certain immunodeficiencies (e.g., Job's syndrome/Hyper-IgE syndrome), it is not the primary or sole immunoglobulin abnormality in **Hyper-IgM Syndrome**.
- In Hyper-IgM syndrome, IgE is typically decreased due to the inability to class switch to IgE.
*Decreased IgA*
- This is true in Hyper-IgM syndrome, but it's only one part of the immunoglobulin profile and not the most comprehensive answer.
- Isolated decreased IgA (Selective IgA Deficiency) is a separate primary immunodeficiency with different clinical manifestations and underlying molecular defects.
*Decreased Interferon gamma*
- Interferon gamma is a cytokine produced by T cells (Th1 cells) and NK cells, important for antiviral and anti-intracellular bacterial immunity.
- While T-cell function can be impaired in immunodeficiencies, a defect in CD40L primarily affects B-cell class switching and antibody production, not directly interferon gamma levels.
Immunopathology US Medical PG Question 5: During an experiment, the immunophenotypes of different cells in a sample are determined. The cells are labeled with fluorescent antibodies specific to surface proteins, and a laser is then focused on the samples. The intensity of fluorescence created by the laser beam is then plotted on a scatter plot. The result shows most of the cells in the sample to be positive for CD8 surface protein. Which of the following cell types is most likely represented in this sample?
- A. Mature cytotoxic T lymphocytes (Correct Answer)
- B. Activated regulatory T lymphocytes
- C. Inactive B lymphocytes
- D. Dendritic cells
- E. Mature helper T lymphocytes
Immunopathology Explanation: ***Mature cytotoxic T lymphocytes***
- **CD8** is a characteristic surface marker for **cytotoxic T lymphocytes**, indicating their immune function in directly killing infected or cancerous cells.
- The "mature" designation implies they have fully developed and are ready to exert their effector functions.
*Activated regulatory T lymphocytes*
- **Regulatory T lymphocytes** are typically identified by the expression of **CD4** and **CD25**, along with the intracellular transcription factor **FOXP3**, not CD8.
- Their primary role is immune suppression, not direct cytotoxicity.
*Inactive B lymphocytes*
- **B lymphocytes** are characterized by the expression of **CD19**, **CD20**, and surface immunoglobulins, which are distinct from the CD8 marker.
- Their main function is antibody production.
*Dendritic cells*
- **Dendritic cells** are primarily **antigen-presenting cells** and are identified by markers such as **CD11c** and **MHC class II molecules**, not CD8.
- While some rare subsets of dendritic cells can express CD8α, it is not their predominant or defining marker.
*Mature helper T lymphocytes*
- **Helper T lymphocytes** are defined by the expression of **CD4** and play a crucial role in coordinating the immune response.
- They do not express CD8, which is characteristic of cytotoxic T cells.
More Immunopathology US Medical PG questions available in the OnCourse app. Practice MCQs, flashcards, and get detailed explanations.
