Immunopathology Practice Questions

Q: Graves disease is an example of which type of immunologic response?

Type I. **Explanation:** **Graves’ Disease** is a classic example of **Type II Hypersensitivity (Antibody-mediated)** [1]. Specifically, it is a sub-type often referred to as "Type V" or "Stimulatory Hypersensitivity." In this condition, B cells produce autoantibodies (Thyroid Stimulating Immunoglobulins - TSI) that bind to the **TSH receptor** on thyroid follicular cells [1]. Instead of causing cell destruction, these antibodies mimic the action of TSH, leading to the overproduction of thyroid hormones (Hyperthyroidism) [1]. **Analysis of Options:** * **Type II (Correct):** Involves antibodies (IgG or IgM) directed against antigens on specific cell surfaces or tissues [1]. In Graves, the "antigen" is the TSH receptor. * **Type I:** This is an **IgE-mediated** immediate hypersensitivity (e.g., Anaphylaxis, Asthma) [1]. It involves mast cell degranulation and is not the mechanism in Graves. * **Type III:** This involves the deposition of **Ag-Ab (Immune) complexes** in tissues, leading to complement activation (e.g., SLE, Post-streptococcal Glomerulonephritis). * **Type IV:** This is **Cell-mediated (Delayed)** hypersensitivity involving T-lymphocytes, not antibodies (e.g., Mantoux test, Contact dermatitis). **High-Yield Clinical Pearls for NEET-PG:** * **Triad of Graves:** Hyperthyroidism, Exophthalmos (due to retro-orbital inflammation), and Pretibial Myxedema. * **Antibody Marker:** TSI (Thyroid Stimulating Immunoglobulin) is the most specific [1]. * **Morphology:** Diffuse hypertrophy and hyperplasia of follicles with **scalloping** of colloid edges. * **Other Type II Examples:** Myasthenia Gravis (blocking antibodies), Goodpasture syndrome, and Hemolytic disease of the newborn [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-214.

Q: Transfusion reactions and erythroblastosis fetalis are examples of which type of hypersensitivity reaction?

Type II hypersensitivity. **Explanation:** **Type II Hypersensitivity (Cytotoxic)** is the correct answer. This reaction is mediated by **IgG or IgM antibodies** directed against antigens present on the surface of specific cells or tissues. When these antibodies bind to the cell surface (e.g., Red Blood Cells), they activate the complement system or lead to Antibody-Dependent Cellular Cytotoxicity (ADCC), resulting in cell lysis or phagocytosis. * In **Transfusion Reactions**, host antibodies attack donor RBC antigens (ABO incompatibility). * In **Erythroblastosis Fetalis**, maternal Rh antibodies cross the placenta and destroy fetal Rh+ RBCs. **Why other options are incorrect:** * **Type I (Immediate):** Mediated by **IgE** and mast cell degranulation (e.g., Anaphylaxis, Asthma). * **Type III (Immune-complex):** Caused by deposition of **antigen-antibody complexes** in tissues, leading to inflammation (e.g., SLE, Post-streptococcal glomerulonephritis). * **Type IV (Delayed):** A **cell-mediated** response involving T-lymphocytes, not antibodies (e.g., Mantoux test, Contact dermatitis). **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Types:** **ACID** (**A**naphylactic, **C**ytotoxic, **I**mmune-complex, **D**elayed). * **Type II Examples:** Goodpasture syndrome, Myasthenia gravis, Rheumatic fever, and Pemphigus vulgaris. * **Coombs Test:** Used specifically to detect Type II reactions in immunohematology. * **Drug-induced Hemolytic Anemia** is also a classic Type II reaction.

Question 1

When tissue pretreated with potassium permanganate is stained with Congo-red stain, the apple-green birefringence is abolished. The tissue is likely to contain which type of amyloid?

Accepted Answer

AA amyloidosis

Answer

AL amyloidosis

Answer

Primary amyloidosis

Answer

Hereditary amyloidosis

Question 2

Which of the following is true about Type II hypersensitivity reactions?

Accepted Answer

Antigen-antibody mediated

Answer

Immune complex mediated

Answer

Arthus phenomenon

Answer

Granulomatous reaction

Question 3

Which of the following is a finding in lymphoid tissues in individuals with common variable hypogammaglobulinemia?

Accepted Answer

Normal B cell count

Answer

Decreased B cell count

Answer

Increased B cell count

Answer

Absent B cells

Question 4

Graves disease is an example of which type of immunologic response?

Accepted Answer

Type I

Answer

Type II

Answer

Type III

Answer

Type IV

Question 5

Toll-like receptors recognize bacterial products and stimulate an immune response by:

Accepted Answer

Transcription of nuclear factor mediated by NF-κB, which recruits cytokines

Answer

Perforin and granzyme mediated apoptosis

Answer

FADD ligand apoptosis

Answer

Cyclin

Question 6

Hereditary angioneurotic edema is due to a deficiency of which of the following?

Accepted Answer

C1 esterase inhibitor

Answer

C1 deficiency

Answer

C2 and C4 deficiency

Answer

C9 deficiency

Question 7

Preformed antibodies cause which type of transplant rejection?

Accepted Answer

Hyperacute rejection

Answer

Acute rejection

Answer

Chronic rejection

Answer

Acute humoral rejection

Question 8

A 36-year-old woman presents with increased trouble swallowing. Physical examination finds hypertension and sclerodactyly. Lab tests find Anti-Scl-70 antibodies. Which of the following biopsies is most characteristic of this disorder?

Accepted Answer

A skin biopsy revealing dermal fibrosis with an absence of adnexal structures

Answer

A conjunctival biopsy revealing noncaseating granulomas

Answer

A peripheral nerve biopsy revealing rare acid-fast bacteria

Answer

A subcutaneous fat biopsy revealing an infiltrate of plasma cells and eosinophils

Question 9

What is the mechanism of acute rheumatic fever?

Accepted Answer

Cross-reactivity with endogenous antigen

Answer

Innocent bystander effect

Answer

Due to toxin secretion by streptococci

Answer

Release of pyrogenic cytokines

Question 10

Transfusion reactions and erythroblastosis fetalis are examples of which type of hypersensitivity reaction?

Accepted Answer

Type II hypersensitivity

Answer

Type I hypersensitivity

Answer

Type III hypersensitivity

Answer

Type IV hypersensitivity

Immunopathology — MCQs

Immunopathology — MCQs

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