Immunopathology Practice Questions

Q: Anti-nuclear antibodies (ANA) seen in Systemic Lupus Erythematosus (SLE) are directed against which of the following?

dsDNA. ### Explanation **Correct Option: A (dsDNA)** Systemic Lupus Erythematosus (SLE) is the prototype autoimmune disease characterized by the production of antibodies against self-antigens, primarily those located within the cell nucleus. **Anti-dsDNA (double-stranded DNA)** antibodies are highly specific for SLE (95-100% specificity) and are a hallmark of the disease [1]. They are directed against the deoxyribonucleic acid backbone. Clinically, their titers correlate with disease activity, particularly the development of **Lupus Nephritis** [2]. **Analysis of Incorrect Options:** * **B. mRNA:** While SLE involves antibodies against various ribonucleoproteins (like Anti-Smith or Anti-U1 RNP), they are directed against proteins complexed with RNA, not typically naked messenger RNA (mRNA) itself. * **C. Nucleolus:** Anti-nucleolar antibodies (producing a nucleolar pattern on immunofluorescence) are more characteristic of **Systemic Sclerosis (Scleroderma)**, specifically associated with antigens like PM-Scl or RNA polymerase I [2]. * **D. Ribosomes:** Anti-ribosomal P antibodies are found in SLE but are less common than anti-dsDNA. They are highly specific for **Neuropsychiatric SLE (Lupus Psychosis)** rather than being the primary target of general ANA screening. **High-Yield Clinical Pearls for NEET-PG:** * **Best Screening Test for SLE:** ANA (High sensitivity, >95%) [1]. * **Most Specific Test for SLE:** Anti-Smith (Anti-Sm) and Anti-dsDNA [2]. * **Drug-Induced Lupus:** Anti-Histone antibodies are the marker of choice. * **Neonatal Lupus/Sjogren’s:** Associated with Anti-Ro (SS-A) and Anti-La (SS-B) [2]. * **Mixed Connective Tissue Disease (MCTD):** Characterized by high titers of Anti-U1 RNP [2].

Q: Hyperacute rejection occurs within:

12 hours. **Explanation:** **Hyperacute rejection** is a Type II hypersensitivity reaction characterized by its rapid onset, occurring within **minutes to a few hours** (typically up to 12–24 hours) after transplantation. It is mediated by **pre-formed antibodies** (IgG) in the recipient's serum against the donor's antigens (usually ABO blood group antigens or HLA Class I antigens). These antibodies bind to the graft endothelium, activating the complement system and leading to immediate thrombosis, fibrinoid necrosis, and graft failure [1]. **Analysis of Options:** * **Option A (12 hours):** This is the correct timeframe. Hyperacute rejection is immediate; if it occurs, it is usually evident before the patient leaves the operating table or within the first few hours post-surgery. * **Option B (2 weeks):** This timeframe is characteristic of **Acute Rejection**, which typically occurs within days to weeks (usually within the first 6 months) [1]. It is primarily T-cell mediated (Type IV hypersensitivity). * **Option C & D (1 month & 3 months):** These timeframes fall under the spectrum of Acute or **Chronic Rejection**. Chronic rejection occurs months to years after transplantation and involves slow, progressive fibrosis and vascular occlusion (e.g., Graft Arteriosclerosis). **High-Yield NEET-PG Pearls:** 1. **Mechanism:** Pre-formed antibodies → Complement activation → Thrombosis [1]. 2. **Gross Appearance:** The graft becomes cyanotic, mottled, and flaccid (often called a "blue kidney") [1]. 3. **Prevention:** It is prevented by **Cross-matching** (testing recipient serum against donor lymphocytes) and ABO typing. 4. **Treatment:** There is no effective treatment once it begins; the graft must be surgically removed [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 241-242.

Q: What is the HLA marker associated with Behcet's syndrome?

HLA-B51. **Explanation:** **HLA-B51** is the strongest genetic risk factor associated with **Behcet’s Syndrome**, a multi-systemic inflammatory disorder characterized by the triad of recurrent oral ulcers, genital ulcers, and uveitis. While the exact pathogenesis is unknown, it is considered an autoinflammatory vasculitis where HLA-B51 plays a role in neutrophil hyper-reactivity. **Analysis of Options:** * **HLA-B27 (Option A):** This is the classic marker for **Seronegative Spondyloarthropathies**, including Ankylosing Spondylitis (strongest association), Reiter’s syndrome (Reactive arthritis), Psoriatic arthritis, and Enteropathic arthritis [1]. * **HLA-DR5 (Option B):** This marker is primarily associated with **Hashimoto’s thyroiditis** and sometimes Kaposi sarcoma. (Note: HLA-DR3 and DR4 are more commonly tested for autoimmune conditions like SLE and Rheumatoid Arthritis). * **HLA-Cw6 (Option D):** This is strongly linked to **Psoriasis vulgaris**, particularly early-onset (Type I) psoriasis. **High-Yield Clinical Pearls for NEET-PG:** * **Behcet’s Syndrome Triad:** Oral ulcers (most common), Genital ulcers (most specific), and Uveitis. * **Pathergy Test:** A unique diagnostic feature where a minor skin prick leads to the formation of a sterile pustule or papule within 48 hours. * **Geographic Distribution:** Highest prevalence is found along the **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. (Basic Pathology) introduces the student to key general principles of pathology, both as a medical science and as a clinical activity with a vital role in patient care. Part 2 (Disease Mechanisms) provides fundamental knowledge about the cellular and molecular processes involved in diseases, providing the rationale for their treatment. Part 3 (Systematic Pathology) deals in detail with specific diseases, with emphasis on the clinically important aspects., pp. 49-50.

Q: Common variable immunodeficiency is due to which of the following?

Defective B cell differentiation. **Explanation:** **Common Variable Immunodeficiency (CVID)** is a primary immunodeficiency characterized by low levels of serum immunoglobulins (IgG, IgA, and often IgM) and a failure to produce specific antibodies following vaccination or infection. **Why Option C is correct:** The hallmark of CVID is not the absence of B cells, but rather a **defect in B cell differentiation** into antibody-secreting plasma cells and memory B cells. While patients usually have a normal or slightly reduced number of peripheral B cells, these cells are functionally immature and cannot undergo terminal differentiation. This leads to hypogammaglobulinemia. **Why other options are incorrect:** * **Option A & B:** Absent or severely reduced B cells (typically <2%) are characteristic of **X-linked Agammaglobulinemia (Bruton’s)**, caused by a mutation in the BTK gene. In CVID, B cell numbers are usually within the normal range or only mildly decreased. * **Option D:** Since the primary pathology is a functional maturation defect rather than a quantitative loss of B cells, "All of the above" is incorrect. **High-Yield Clinical Pearls for NEET-PG:** * **Age of Onset:** Unlike Bruton’s (infancy), CVID typically presents in the **2nd–3rd decade** of life (bimodal peaks: 1-5 years and 18-30 years). * **Clinical Features:** Recurrent sinopulmonary infections (H. influenzae, S. pneumoniae), increased risk of **Giardiasis**, and autoimmune disorders. * **Malignancy Risk:** Significant predisposition to **Non-Hodgkin Lymphoma** and Gastric Carcinoma. * **Diagnosis:** Low IgG (at least 2 SD below mean) plus low IgA and/or IgM, with poor response to vaccines.

Question 1

Anti-nuclear antibodies (ANA) seen in Systemic Lupus Erythematosus (SLE) are directed against which of the following?

Accepted Answer

dsDNA

Answer

mRNA

Answer

Nucleolus

Answer

Ribosomes

Question 2

All are true regarding Severe Combined Immunodeficiency (SCID) except:

Accepted Answer

Toxicity of leucocytes due to accumulation of cyclic adenosine monophosphate (cAMP)

Answer

Due to deficiency of adenosine deaminase

Answer

Both cellular and humoral immunity are affected

Answer

Bone marrow transplantation is a treatment option

Question 3

Anti-Ro antibody is associated with which of the following conditions?

Accepted Answer

Neonatal Lupus

Answer

Systemic Lupus Erythematosus (SLE)

Answer

Scleroderma

Answer

Mixed Connective Tissue Disease (MCTD)

Question 4

Which cell type is primarily involved in immunity against parasitic infections?

Accepted Answer

Eosinophil

Answer

Neutrophil

Answer

Basophil

Answer

Lymphocyte

Question 5

Hyperacute rejection occurs within:

Accepted Answer

12 hours

Answer

2 weeks

Answer

1 month

Answer

3 months

Question 6

CD4 is not important for which of the following?

Accepted Answer

Cytotoxicity of T cells

Answer

Antibody production

Answer

Memory B cells

Answer

Opsonization

Question 7

An 18-year-old man is evaluated for possible immunodeficiency disease due to a lifelong history of chronic lung infections, recurrent otitis media, and multiple episodes of bacterial meningitis. Although total IgG is normal, the patient has a selective deficiency of IgG2. An associated deficiency of which of the following other substances may produce anaphylaxis when blood products are given to such individuals?

Accepted Answer

IgA

Answer

C3

Answer

C4

Answer

IgE

Question 8

What is the HLA marker associated with Behcet's syndrome?

Accepted Answer

HLA-B51

Answer

HLA-B27

Answer

HLA-DR5

Answer

HLA-CW6

Question 9

Common variable immunodeficiency is due to which of the following?

Accepted Answer

Defective B cell differentiation

Answer

Absent B cells

Answer

Reduced number of B cells

Answer

All of the above

Question 10

Acute graft rejection typically occurs within what timeframe?

Accepted Answer

3 months

Answer

3 hours

Answer

3 days

Answer

3 years

Immunopathology — MCQs

Immunopathology — MCQs

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