Immunopathology Practice Questions

Q: A mother donated a kidney to her daughter who has chronic renal failure. What type of graft does this represent?

Allograft. **Explanation:** The correct answer is **Allograft**. This classification is based on the genetic relationship between the donor and the recipient. 1. **Why Allograft is correct:** An allograft (or homograft) is a transplant between two genetically non-identical members of the same species. Since a mother and daughter share 50% of their genes but are not genetically identical, the transplant is classified as an allograft. This is the most common type of organ transplantation in clinical practice. 2. **Why other options are incorrect:** * **Isograft (Syngeneic graft):** This occurs between genetically identical individuals, such as **monozygotic (identical) twins**. In this case, there is no risk of rejection. * **Xenograft (Heterograft):** This involves a transplant between members of **different species** (e.g., a porcine/pig heart valve transplanted into a human). * **Autograft:** This is a transplant where the donor and recipient are the **same individual** (e.g., a skin graft from the thigh to the arm or a saphenous vein used for CABG). **High-Yield Clinical Pearls for NEET-PG:** * **Hyperacute Rejection:** Occurs within minutes to hours due to pre-formed cytotoxic antibodies (Type II Hypersensitivity). * **Acute Rejection:** Occurs within days to weeks; primarily mediated by T-cells (Type IV Hypersensitivity). * **Chronic Rejection:** Occurs months to years later, characterized by fibrosis and intimal thickening of graft vessels. * **HLA Matching:** The most important HLA loci for renal transplant success are **HLA-A, HLA-B, and HLA-DR**.

Q: Which CD marker is associated with cytotoxic T-lymphocytes?

CD 8. ### Explanation **Correct Option: B (CD 8)** Cytotoxic T-lymphocytes (CTLs) are a subtype of T-cells responsible for the direct destruction of virally infected cells and tumor cells [1]. They are characterized by the expression of the **CD8** surface marker. These cells recognize antigens presented by **MHC Class I** molecules (Rule of 8: 8 × 1 = 8) [2]. Upon activation, they release perforins and granzymes to induce apoptosis in target cells. **Analysis of Incorrect Options:** * **CD 4 (Option A):** This marker is associated with **Helper T-lymphocytes (Th cells)** [3]. They recognize antigens presented by **MHC Class II** molecules (Rule of 8: 4 × 2 = 8) and coordinate the immune response by secreting cytokines. * **CD 21 (Option B):** This is a marker for **B-lymphocytes**. It also serves as the receptor for the **Epstein-Barr Virus (EBV)**, facilitating its entry into B-cells (leading to Infectious Mononucleosis). * **CD 45 (Option D):** Known as the **Leukocyte Common Antigen (LCA)**, it is expressed on all hematopoietic cells (except mature erythrocytes and platelets). It is used in immunohistochemistry to differentiate lymphomas from carcinomas. **High-Yield Clinical Pearls for NEET-PG:** * **CD3:** The pan-T-cell marker (present on both CD4+ and CD8+ cells) [3]. * **CD19, CD20, CD21:** Classic B-cell markers. * **CD16/CD56:** Markers for Natural Killer (NK) cells. * **CD15/CD30:** Positive in Reed-Sternberg cells (Hodgkin Lymphoma), except in the lymphocyte-predominant subtype. * **CD34:** Marker for hematopoietic stem cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 240. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 318-319. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 198-199.

Q: All are true about Wiskott-Aldrich syndrome except?

Large size platelets. **Explanation:** Wiskott-Aldrich Syndrome (WAS) is an **X-linked recessive** immunodeficiency caused by a mutation in the **WASP gene**, which leads to defective actin cytoskeleton reorganization in hematopoietic cells. **Why Option C is the correct answer (The "Except"):** In Wiskott-Aldrich Syndrome, platelets are characteristically **small in size** (microthrombocytopenia) and reduced in number. This is a high-yield diagnostic feature, as it is one of the few conditions where small platelets are seen. Large platelets (Option C) are seen in conditions like Bernard-Soulier Syndrome or ITP, making this statement false regarding WAS. **Analysis of other options:** * **Option A (Bloody diarrhea):** Due to profound thrombocytopenia and platelet dysfunction, infants often present with petechiae, purpura, and bloody diarrhea shortly after birth. * **Option B (Immunoglobulin profile):** The classic pattern is **low IgM**, normal to high IgG, and **elevated IgA and IgE**. This reflects the progressive decline in humoral and cellular immunity. * **Option D (Atopic dermatitis):** Severe, refractory eczema is a hallmark clinical feature of the classic triad. **NEET-PG High-Yield Pearls:** * **The Classic Triad:** (1) Thrombocytopenia/Bleeding, (2) Eczema, (3) Recurrent infections (due to T-cell and B-cell deficiency). * **Genetics:** X-linked recessive; WASP gene maps to **Xp11.22**. * **Complications:** Increased risk of **Non-Hodgkin Lymphoma** (especially EBV-related) and autoimmune hemolytic anemia. * **Treatment:** Bone marrow transplant is the definitive curative treatment.

Q: Which of the following is NOT a Type-III hypersensitivity reaction?

Pemphigus vulgaris. **Explanation:** The correct answer is **D. Pemphigus vulgaris**. **1. Why Pemphigus vulgaris is the correct answer:** Pemphigus vulgaris is a **Type-II hypersensitivity reaction**. It is mediated by IgG autoantibodies directed against **Desmoglein-1 and Desmoglein-3** (cell surface antigens) in the epidermis. This leads to acantholysis (loss of cell-to-cell adhesion), resulting in intraepidermal blisters. In contrast, Type-III hypersensitivity involves the deposition of **circulating antigen-antibody (immune) complexes** in tissues, leading to complement activation and inflammation. **2. Analysis of Incorrect Options (Type-III Reactions):** * **Polyarteritis nodosa (PAN):** A classic Type-III reaction where immune complexes (often involving Hepatitis B surface antigen) deposit in small to medium-sized arteries, causing necrotizing vasculitis. * **Post-streptococcal glomerulonephritis (PSGN):** Occurs when streptococcal antigen-antibody complexes deposit in the glomerular basement membrane, leading to a "lumpy-bumpy" appearance on immunofluorescence. * **Epstein-Barr virus (EBV) infections:** Certain manifestations of EBV, such as associated vasculitis or immune-complex mediated nephritis, are classified under Type-III hypersensitivity. **3. NEET-PG Clinical Pearls:** * **Type-II Mnemonic:** "Cytotoxic" (Antibody vs. Cell Surface). Examples: Myasthenia Gravis, Goodpasture syndrome, Rheumatic fever. * **Type-III Mnemonic:** "Immune Complex" (Soluble antigen + Antibody). Examples: SLE, Arthus reaction, Serum sickness, Farmer’s Lung. * **High-Yield Fact:** Pemphigus vulgaris shows a **"row of tombstones"** appearance on histology and a **"fishnet"** pattern on direct immunofluorescence (DIF).

Q: Mikulicz's disease is classified as which of the following?

An autoimmune disease. **Explanation:** **Mikulicz’s Disease (MD)** is characterized by the chronic, painless, symmetrical enlargement of the lacrimal and salivary glands (parotid and submandibular). 1. **Why the correct answer is right:** Mikulicz’s disease is now recognized as a part of **IgG4-related systemic disease (IgG4-RD)**. It is an **autoimmune condition** characterized by elevated serum IgG4 levels and extensive infiltration of IgG4-positive plasma cells and lymphocytes into the affected glands, leading to fibrosis and enlargement. Historically, it was confused with Sjögren’s syndrome, but it is distinct because it lacks the typical anti-Ro (SS-A) and anti-La (SS-B) antibodies and responds well to steroid therapy. 2. **Why the incorrect options are wrong:** * **Inflammatory disease (A):** While inflammation occurs, it is the *result* of an underlying autoimmune process. In NEET-PG, if "autoimmune" is an option for IgG4-related conditions, it is the more specific and correct classification. * **Neoplastic disease (B):** Although the gland enlargement can mimic a tumor (pseudotumor), the process is benign and reactive rather than a monoclonal cellular malignancy. * **Viral infection (D):** While viruses like Mumps or HIV can cause parotid swelling, Mikulicz’s disease is not caused by a viral pathogen. **High-Yield Clinical Pearls for NEET-PG:** * **Mikulicz’s Syndrome vs. Disease:** *Syndrome* refers to gland enlargement secondary to other diseases (e.g., Sarcoidosis, Leukemia, Lymphoma), whereas *Disease* is the primary idiopathic/autoimmune form. * **Histopathology:** Shows "Lymphepithelial lesions" and "Storiform fibrosis." * **Treatment:** Systemic **Corticosteroids** are the first-line treatment and usually result in a dramatic reduction in gland size. * **Key Association:** Always look for elevated **IgG4 levels** in the clinical vignette.

Question 1

L.E. Cell phenomenon in peripheral blood is seen in:

Accepted Answer

Systemic Lupus Erythematosus

Answer

Rheumatic heart disease

Answer

Infective endocarditis

Answer

Ischemic heart disease

Question 2

A mother donated a kidney to her daughter who has chronic renal failure. What type of graft does this represent?

Accepted Answer

Allograft

Answer

Isograft

Answer

Xenograft

Answer

Autograft

Question 3

Which CD marker is associated with cytotoxic T-lymphocytes?

Accepted Answer

CD 8

Answer

CD 4

Answer

CD 21

Answer

CD 45

Question 4

Autoimmunity is caused by which of the following mechanisms?

Accepted Answer

Failure of negative selection of T cells in the thymus

Answer

Pressure of forbidden clones

Answer

Expression of cryptic antigens

Answer

Inappropriate expression of MHC proteins

Question 5

What is the first line of defense against tumors and viruses?

Accepted Answer

NK cell

Answer

T cell

Answer

Histiocyte

Answer

Macrophage

Question 6

All are true about Wiskott-Aldrich syndrome except?

Accepted Answer

Large size platelets

Answer

Bloody diarrhea during infancy

Answer

Low IgM and elevated IgA and IgE

Answer

Atopic dermatitis

Question 7

A 7-month-old boy has had multiple bouts of otitis media, sinusitis, bronchitis, oral candidiasis, and multiple viral infections. Cessation of the recurrent infections follows successful engraftment of a bone marrow transplant. What is the basis of the clinical improvement?

Accepted Answer

Maturation of donor lymphoid progenitor cells.

Answer

Direct transfusion of antibody-producing B cells.

Answer

Direct transfusion of donor CD4+ and CD8+ lymphocytes.

Answer

Donor suppression of recipient cytotoxic T cells.

Question 8

A neonate develops spastic contractions on the second postpartum day. Laboratory studies show hypocalcemia. MRI studies demonstrate aplasia of the thymus and parathyroid glands. What is the appropriate diagnosis?

Accepted Answer

DiGeorge syndrome

Answer

Transient hypogammaglobulinemia of infancy

Answer

Adenosine deaminase deficiency

Answer

Common variable immunodeficiency

Question 9

Which of the following is NOT a Type-III hypersensitivity reaction?

Accepted Answer

Pemphigus vulgaris

Answer

Polyarteritis nodosa

Answer

Post-streptococcal glomerulonephritis

Answer

Epstein-Barr virus infections

Question 10

Mikulicz's disease is classified as which of the following?

Accepted Answer

An autoimmune disease

Answer

An inflammatory disease

Answer

A neoplastic disease

Answer

A viral infection

Immunopathology — MCQs

Immunopathology — MCQs

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