Immunopathology Practice Questions

Q: A person was brought to the emergency department with facial swelling, itching, and hypotension following a bee sting. The mentioned clinical features are due to the increase in which immunoglobulin?

IgE. IgE - The symptoms of **facial swelling, itching, and hypotension** following a bee sting are characteristic of an immediate hypersensitivity reaction, specifically **anaphylaxis**, which is predominantly mediated by **IgE antibodies** [1]. - **IgE** binds to mast cells and basophils, and upon re-exposure to the allergen (bee venom), triggers the release of potent inflammatory mediators like **histamine**, causing vasodilation, increased vascular permeability, and smooth muscle contraction [1], . *IgG* - **IgG** antibodies are primarily involved in secondary immune responses, conferring long-term immunity, and neutralizing toxins and viruses [1]. - While IgG can be involved in some hypersensitivity reactions (Type II and Type III), it is not the primary immunoglobulin responsible for the acute, systemic symptoms of **anaphylaxis** from a bee sting [1]. *IgA* - **IgA** is the main immunoglobulin found in mucosal secretions, such as those in the gastrointestinal, respiratory, and genitourinary tracts, providing mucosal immunity. - It does not play a significant role in immediate hypersensitivity reactions or the systemic symptoms described in this scenario. *IgM* - **IgM** is the first antibody produced during a primary immune response and is important for activating the complement system and agglutinating antigens [1]. - It is not directly implicated in the pathogenesis of **Type I hypersensitivity reactions** like the anaphylactic response to a bee sting. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-213.

Q: Which of the following cytokines plays the most crucial role in mediating the inflammatory response and tissue damage in gonococcal arthritis?

IL-1β. ***IL-1β*** - **IL-1β** is the most crucial cytokine mediating inflammatory response and tissue damage specifically in **gonococcal arthritis** - Neisseria gonorrhoeae infection triggers potent **IL-1β production** through complement activation and bacterial lipooligosaccharide (LOS) [1] - IL-1β drives the production of **matrix metalloproteinases (MMPs)** and other degradative enzymes, leading to **cartilage and bone destruction** - It amplifies the inflammatory cascade by inducing other pro-inflammatory cytokines and chemokines [1] - Experimental models show that **IL-1β blockade significantly reduces joint damage** in gonococcal infections *IL-8* - **IL-8** (CXCL8) is a critical **neutrophil chemokine** that causes the characteristic massive neutrophil infiltration in gonococcal arthritis [1] - While essential for leukocyte recruitment and the purulent synovial fluid seen in this condition, it is primarily a **chemotactic mediator** rather than the main driver of tissue destruction [1] *IL-6* - **IL-6** is a pro-inflammatory cytokine involved in the **acute phase response** and systemic inflammatory features [1] - It contributes to fever, synovitis, and B-cell responses during infection - However, its role in directly mediating joint tissue damage in gonococcal arthritis is **secondary** to IL-1β *TNF-α* - **TNF-α** is a potent pro-inflammatory cytokine important in many forms of arthritis, particularly **rheumatoid arthritis** and chronic inflammatory conditions [1] - While it does contribute to inflammation in septic arthritis, in **gonococcal arthritis specifically**, the cytokine profile is **dominated by IL-1β and IL-8** - The pathophysiology of gonococcal infection differs from other bacterial arthritides where TNF-α may play a more central role **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 97-99.

Q: Acute graft rejection occurs within?

< 6 months. ***< 6 months*** - **Acute graft rejection** typically occurs within the first few **weeks to months** after transplantation due to a T-cell mediated immune response against the donor organ [1]. - While it can manifest at any time, the majority of cases occur within the **first 6 months** post-transplant, making this the most appropriate time frame [1]. *Few minutes* - Rejection presenting within minutes of transplantation is characteristic of **hyperacute rejection**, which is caused by pre-existing **donor-specific antibodies** [1]. - This rapid form of rejection is mediated by **complement activation** and leads to immediate graft failure [1]. *6-12 months* - Rejection occurring in this timeframe might still be acute, but the peak incidence is generally earlier. - Rejection presenting after 6 months is often categorized as **late acute rejection** or may start to transition towards signs of chronic rejection, which occurs over a longer period. *Few hours* - Rejection within a few hours could be a very early form of **acute rejection** or a delayed presentation of **hyperacute rejection** [1]. - However, the classic presentation of acute rejection is more prolonged than a few hours, usually developing over days to weeks. **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: Rheumatoid factor is an antibody of which class -

IgM. ***IgM*** - **Rheumatoid factor (RF)** is typically an **IgM autoantibody** directed against the Fc region of IgG. - While other isotypes of RF (IgG, IgA) exist, **IgM RF** is the most common form detected in serological tests for **rheumatoid arthritis**. *IgD* - **IgD** antibodies are found in small amounts in the serum and are primarily located on the surface of **B lymphocytes**, where they function as antigen receptors. - They are not associated with autoantibodies like **rheumatoid factor**. *IgE* - **IgE** antibodies are primarily involved in **allergic reactions** and defense against parasites [1]. - High levels of IgE are characteristic of **atopic diseases** such as asthma and allergic rhinitis, not autoimmune conditions like rheumatoid arthritis [1]. *IgG* - While IgG is the most abundant immunoglobulin in serum and plays a crucial role in immune defense, **rheumatoid factor** itself is usually an **IgM or IgA antibody** that targets the Fc portion of IgG. - Therefore, IgG is the *target* of RF often, but **not the isotype of RF itself** in the most common clinical assay. **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. 171-172.

Q: HLA associated with Rheumatoid arthritis is?

HLA-DR4. ***HLA-DR4*** - **HLA-DR4** is the **MHC Class II allele** most strongly associated with an increased risk and severity of **rheumatoid arthritis**, particularly in populations of European descent [2]. - This association is particularly relevant for the development of antibodies against **citrullinated proteins (ACPAs)**, a hallmark of more aggressive disease [1]. *HLA CW6* - **HLA CW6** is strongly associated with **psoriasis** and **psoriatic arthritis**, not rheumatoid arthritis. - It plays a role in the immune system's response in these conditions, distinct from the autoimmune mechanisms of rheumatoid arthritis. *HLAB8* - **HLA-B8** is associated with several autoimmune diseases, including **celiac disease**, **myasthenia gravis**, and Sjögren's syndrome, but not primarily with rheumatoid arthritis. - It reflects a broader predisposition to autoimmunity rather than a specific link to RA. *HLAB27* - **HLA-B27** is highly associated with **seronegative spondyloarthropathies**, such as **ankylosing spondylitis** and **reactive arthritis** [3]. - Its presence indicates a strong genetic predisposition for these conditions, which differ clinically and immunologically from rheumatoid arthritis [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1212. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1212-1214. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1214-1215.

Q: Rheumatoid factor is directed against ?

IgG. ***IgG*** - **Rheumatoid factor (RF)** is typically an **IgM antibody** that targets the **Fc portion of human IgG**. - This binding leads to the formation of **immune complexes**, which contribute to the inflammation and joint damage seen in **rheumatoid arthritis (RA)** [1]. *IgA* - While IgA can be involved in some autoimmune processes, it is **not the primary target** of rheumatoid factor. - Elevated IgA levels can be seen in various conditions, but **IgA is not the antigen** that RF binds to. *IgM* - **IgM is the class of antibody** that the rheumatoid factor itself usually belongs to (i.e., RF is often an IgM antibody). - However, RF is **not directed against IgM**; it is directed against another immunoglobulin class. *IgD* - **IgD** has a less defined role in the systemic immune response compared to other immunoglobulin classes. - It is **not the target** of rheumatoid factor and is not commonly implicated in the pathogenesis of rheumatoid arthritis in this manner. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1212.

Question 1

A person was brought to the emergency department with facial swelling, itching, and hypotension following a bee sting. The mentioned clinical features are due to the increase in which immunoglobulin?

Accepted Answer

IgE

Answer

IgG

Answer

IgA

Answer

IgM

Question 2

Which cell acts as the primary effector cell in type IV (delayed-type) hypersensitivity reactions?

Accepted Answer

Macrophage

Answer

Neutrophil

Answer

Dendritic cell

Answer

Cytotoxic T cell

Question 3

Which of the following cytokines plays the most crucial role in mediating the inflammatory response and tissue damage in gonococcal arthritis?

Accepted Answer

IL-1β

Answer

TNF-α

Answer

IL-8

Answer

IL-6

Question 4

Acute graft rejection occurs within?

Accepted Answer

< 6 months

Answer

Few minutes

Answer

6-12 months

Answer

Few hours

Question 5

Rheumatoid factor is an antibody of which class -

Accepted Answer

IgM

Answer

IgD

Answer

IgE

Answer

IgG

Question 6

A 20-year-old woman complains of weakness that is worse in the afternoon, worse during prolonged activity, and improved by rest. When fatigued, the patient is unable to hold her head up or chew her food. She often notes diplopia when driving home from work. On physical examination, she has no loss of reflexes, sensation, or coordination. Which of the following is the likely pathogenesis of this disease?

Accepted Answer

Autoantibodies directed against the postsynaptic acetylcholine receptor causing neuromuscular transmission failure

Answer

Destruction of anterior horn cells by virus

Answer

Demyelinating disease

Answer

Progressive muscular atrophy caused by spinal degeneration

Question 7

HLA associated with Rheumatoid arthritis is?

Accepted Answer

HLA-DR4

Answer

HLA-Cw6

Answer

HLA-B8

Answer

HLA-B27

Question 8

Human leukocyte antigen (HLA) DR4 occurs in about 70% of patients with rheumatoid arthritis. HLA-DR4 is encoded in the major histocompatibility complex (MHC) region on:

Accepted Answer

Chromosome 6

Answer

Chromosome 22

Answer

Chromosome 9

Answer

Chromosome 18

Question 9

Rheumatoid factor is directed against ?

Accepted Answer

IgG

Answer

IgA

Answer

IgM

Answer

IgD

Question 10

Which of the following statements regarding rejection of solid organ transplants is true?

Accepted Answer

Hyperacute rejection begins in the operating room with reperfusion of the transplanted organ

Answer

Most immunosuppressive medications are used to prevent chronic rejection

Answer

The major cause of graft failure is acute rejection

Answer

Liver transplants are especially susceptible to hyperacute rejection

Immunopathology — MCQs

Immunopathology — MCQs

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