Immunopathology Practice Questions

Q: Which cytokine has a predominant anti-inflammatory action?

TGF-beta. **Explanation:** The balance between pro-inflammatory and anti-inflammatory cytokines is crucial for immune homeostasis. **TGF-beta (Transforming Growth Factor-beta)** is a potent **anti-inflammatory** cytokine. It functions by inhibiting the proliferation and activation of lymphocytes (T-cells and B-cells) and suppressing the production of pro-inflammatory cytokines [1]. Additionally, it plays a vital role in tissue repair and fibrosis by stimulating collagen synthesis [1]. Along with **IL-10**, TGF-beta is considered a primary mediator of immune tolerance and resolution of inflammation. **Analysis of Incorrect Options:** * **Interleukin 6 (IL-6):** A classic **pro-inflammatory** cytokine. It is a major inducer of the "acute phase response" in the liver (CRP production) and is involved in fever and the transition from innate to adaptive immunity [1]. * **GM-CSF (Granulocyte-Macrophage Colony-Stimulating Factor):** A growth factor that stimulates the bone marrow to produce granulocytes and monocytes [1]. It acts as a **pro-inflammatory** mediator by enhancing the survival and activation of mature macrophages and neutrophils. * **TNF-Alpha (Tumor Necrosis Factor-alpha):** A "master" **pro-inflammatory** cytokine produced primarily by macrophages. It mediates septic shock, induces endothelial activation, and recruits leukocytes to sites of infection [1]. **High-Yield Clinical Pearls for NEET-PG:** * **The "Anti-inflammatory Duo":** Always remember **IL-10 and TGF-beta** as the primary anti-inflammatory cytokines. * **TGF-beta Dual Role:** While anti-inflammatory, it is the most important cytokine for **fibrosis** (stimulates fibroblasts) [1]. * **IL-1 and TNF-alpha:** These are the primary mediators of acute inflammation [1]. * **IL-8:** The most potent chemotactic factor for **neutrophils**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 111-116.

Q: Memory T cells can be identified by using which of the following markers?

CD45RO. **Explanation:** The correct answer is **CD45RO**. **1. Why CD45RO is correct:** CD45 (also known as Leukocyte Common Antigen) is a transmembrane protein tyrosine phosphatase essential for T-cell activation. It exists in several isoforms due to alternative splicing of exons 4, 5, and 6 (A, B, and C). * **CD45RO** is the shortest isoform (lacking exons A, B, and C). It is specifically expressed on **Memory T cells** [1] and activated effector T cells. Its structure allows for more efficient interaction with the T-cell receptor (TCR) complex, facilitating a rapid secondary immune response upon re-exposure to an antigen. **2. Why the other options are incorrect:** * **CD45RA:** This isoform contains the 'A' exon. It is the classic marker for **Naive T cells** (T cells that have not yet encountered their specific antigen) [1]. * **CD45RB and CD45RC:** These isoforms are typically expressed on naive B cells, subsets of T cells, and other myeloid cells. They are not specific markers used to differentiate memory T cells in a clinical or examination context. **3. NEET-PG High-Yield Pearls:** * **The Switch:** When a Naive T cell (CD45RA+) encounters an antigen, it undergoes activation and "switches" its expression to the memory phenotype (**CD45RO+**). * **CD4 vs. CD8:** Both Helper (CD4+) and Cytotoxic (CD8+) T cells can be subdivided into Naive and Memory subsets using these markers. * **Clinical Correlation:** In certain immunodeficiencies or lymphomas, the ratio of CD45RA to CD45RO can be diagnostically significant. * **Mnemonic:** "R**O**" for **O**ld (Memory) cells; "R**A**" for **A**mateur (Naive) cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, p. 198.

Q: What is the normal CD4:CD8 ratio?

2:1. **Explanation:** In a healthy individual, the normal **CD4:CD8 ratio is approximately 2:1** [1]. This ratio represents the balance between T-helper cells (CD4+), which orchestrate the immune response, and T-cytotoxic cells (CD8+), which directly kill infected or malignant cells. In peripheral blood, CD4+ T cells typically make up about 60–70% of the T-cell population, while CD8+ T cells account for about 30%. **Analysis of Options:** * **Option B (2:1):** This is the physiological baseline [1]. Maintaining this ratio is crucial for effective immune surveillance without excessive immunosuppression or autoimmunity. * **Option A (3:1):** While some healthy individuals may have a slightly higher ratio, 2:1 is the standard clinical benchmark used in pathology and immunology. * **Options C & D (1:2 and 1:3):** These represent an **inverted ratio**. A ratio of less than 1:1 is clinically significant and pathological, indicating either a depletion of CD4 cells or an expansion of CD8 cells [1]. **Clinical Pearls for NEET-PG:** 1. **HIV/AIDS:** The hallmark of HIV progression is the progressive destruction of CD4+ T cells, leading to an **inverted CD4:CD8 ratio** (often <0.5) [1]. Monitoring this ratio is vital for staging the disease. 2. **Other Causes of Inversion:** Apart from HIV, an inverted ratio can be seen in viral infections (EBV, CMV), aging, chronic inflammation, and certain primary immunodeficiencies. 3. **Sarcoidosis:** A high-yield contrast is that in Sarcoidosis, the CD4:CD8 ratio in **Bronchoalveolar Lavage (BAL) fluid** is typically significantly **increased (>3.5:1)**, aiding in diagnosis. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 555-556.

Question 1

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 2

Acute auto-graft rejection occurs within what timeframe?

Accepted Answer

Less than 6 months

Answer

A few hours

Answer

Less than 1 month

Answer

6-12 months

Question 3

Which of the following is a Type 2 Hypersensitivity reaction?

Accepted Answer

Autoimmune Hemolytic anaemia

Answer

Chronic Kidney Rejection episode

Answer

Arthus reaction

Answer

Mitsuda reaction

Question 4

Which cytokine is responsible for activating macrophages and their conversion into epithelioid cells or giant cells?

Accepted Answer

Interferon-gamma (IFN-gamma)

Answer

Interleukin-2 (IL-2)

Answer

Interleukin-17 (IL-17)

Answer

Tumor Necrosis Factor-alpha (TNF-alpha)

Question 5

Which cytokine has a predominant anti-inflammatory action?

Accepted Answer

TGF-beta

Answer

Interleukin 6

Answer

GM-CSF

Answer

TNF-Alpha

Question 6

Memory T cells can be identified by using which of the following markers?

Accepted Answer

CD45RO

Answer

CD45RA

Answer

CD45RB

Answer

CD45RC

Question 7

A 35-year-old woman with end-stage renal disease of unknown etiology is transplanted with a cadaver kidney. The patient develops oliguria shortly after transplantation and a renal biopsy shows immediate (hyperacute) rejection. Immunosuppression improves renal function. Which of the following represents the principle target for immune attack directed against this patient's allograft?

Accepted Answer

ABO antigens

Answer

Bacterial antigens

Answer

Glomerular basement membrane antigens

Answer

b2-Microglobulin

Question 8

Candida infections are commonly seen in patients with which of the following conditions?

Accepted Answer

Myeloperoxidase deficiency

Answer

Chronic granulomatous disease

Answer

Chediak-Higashi syndrome

Answer

Lazy leukocyte syndrome

Question 9

Which of the following is NOT affected in Graft-Versus-Host reaction?

Accepted Answer

Lung

Answer

Skin

Answer

Gastrointestinal tract

Answer

Liver

Question 10

What is the normal CD4:CD8 ratio?

Accepted Answer

2:1

Answer

3:1

Answer

1:2

Answer

1:3

Immunopathology — MCQs

Immunopathology — MCQs

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