Immunopathology Practice Questions

Q: Which of the following HLA types is most commonly associated with rheumatoid arthritis?

HLA DR4. ***Correct: HLA DR4*** - **HLA-DR4** is the **most strongly associated HLA type with rheumatoid arthritis** globally and is found in a majority of affected individuals. - This association is primarily with the **"shared epitope" alleles within the HLA-DRB1 locus** (particularly HLA-DRB1*04), contributing to genetic susceptibility and disease severity. - The shared epitope hypothesis explains how specific amino acid sequences in the HLA-DR beta chain increase RA risk. *Incorrect: HLA DR8* - While other HLA-DR types may show minor associations in certain populations or with specific disease manifestations, **DR8 is not the primary or most common association** for rheumatoid arthritis. - Its association, if any, is **significantly weaker** compared to HLA-DR4. *Incorrect: HLA DQ1* - **HLA-DQ1** (also known as HLA-DQB1*05 and DQB1*06) is a class II MHC molecule, but it is **not the primary HLA type associated with rheumatoid arthritis**. - While HLA-DQ genes can contribute to autoimmune disease susceptibility, **HLA-DRB1 alleles, particularly DR4**, have a stronger and more consistent link to RA. *Incorrect: HLA B27* - **HLA-B27** is a well-known genetic marker, but it is **classically associated with seronegative spondyloarthropathies** like ankylosing spondylitis, psoriatic arthritis, and reactive arthritis—**not rheumatoid arthritis**. - Its presence is a strong indicator for conditions characterized by **axial skeletal involvement and enthesitis**, differentiating them from RA, which primarily affects peripheral joints symmetrically.

Q: Hypersensitivity pneumonitis is classically an immunologically mediated inflammatory reaction. Which type of hypersensitivity is primarily involved?

Type IV hypersensitivity. ***Immune complex mediated hypersensitivity*** - Hypersensitivity pneumonitis is indeed primarily characterized by **immune complex-mediated inflammation** in response to inhaled antigens [1][2]. - This condition often leads to a **Type III hypersensitivity reaction**, where immune complexes form and trigger inflammation in the lung tissues [1][2]. *Cell mediated hypersensitivity* - While cell-mediated mechanisms are important in many immune responses, hypersensitivity pneumonitis mainly involves **immune complex formation** [2]. - This type predominantly reflects a **Type III hypersensitivity** rather than the typical **Type IV** attributed to cell-mediated reactions [3], though T-cell mediated reactions may also contribute [2]. *Allergic reaction* - Allergic reactions generally refer to **IgE-mediated hypersensitivity**, which typically involves immediate responses and mast cell activation [3]. - Hypersensitivity pneumonitis is not an **immediate hypersensitivity** but rather a delayed immune response to **chronic antigen exposure** [2]. *Type II hypersensitivity* - Type II hypersensitivity is mediated by **IgG or IgM antibodies** targeting specific cells or tissues, causing cell destruction [3]. - This is **not applicable** to hypersensitivity pneumonitis, which involves **immune complexes** accumulating in response to environmental antigens [1][2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 214-215. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, pp. 701-702. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210.

Q: Histamine in anaphylaxis is secreted by which of the following cells?

Mast cells. ***Mast cells*** - Mast cells are the primary cells responsible for the secretion of **histamine** during anaphylaxis, leading to rapid allergic responses [2][4]. - They are located in **tissues** and are involved in **immediate hypersensitivity reactions** by releasing various mediators upon activation [1][2]. *Basophils* - While basophils do contain **histamine**, they play a lesser role in acute anaphylaxis as compared to mast cells [1]. - Basophils are more associated with chronic allergic reactions rather than the **immediate release** observed in anaphylaxis [1]. *Macrophages* - Macrophages are primarily involved in **phagocytosis** and immune response but do not secrete significant amounts of histamine. - They release cytokines and other mediators but are not key players in **histamine-dependent** anaphylactic reactions. *B-cells* - B-cells are crucial for the production of **antibodies** but do not secrete histamine at all. - They are involved in **adaptive immunity** and do not play a direct role in **anaphylaxis** mechanisms [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 210-211. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 211-212. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 212-213. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Inflammation and Repair, pp. 93-94.

Q: The hypersensitivity reaction involved in the hyperacute rejection of a renal transplant is:

Type II. ***Type II*** - Hyperacute rejection is primarily mediated by **antibody-mediated mechanisms**, indicative of Type II hypersensitivity [2]. - It involves pre-existing **IgG antibodies** that react against donor renal graft antigen, leading to rapid graft destruction [1]. *Type I* - Type I hypersensitivity is associated with **allergic reactions** involving **IgE antibodies**, not relevant to transplant rejection [2]. - Typically involves conditions like **anaphylaxis** or **asthma**, which are unrelated to hyperacute rejection scenarios. *Type IV* - Type IV hypersensitivity is cell-mediated and typically manifests as **delayed-type hypersensitivity**, not acute rejection. - It involves **T cells** and does not play a role in the immediate immune response seen in hyperacute rejection. *Type III* - Type III hypersensitivity involves the formation of immune complexes, leading to conditions like **serum sickness**, not hyperacute rejection. - This type of reaction is usually more relevant in **chronic inflammatory conditions** rather than immediate transplant rejections. **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. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210.

Q: Which antigen is most critical in initiating graft rejection?

HLA - Antigen. ***MHC - molecule*** - The **Major Histocompatibility Complex (MHC)** molecules are critical in presenting **antigens** to T-cells, which initiates the graft rejection process [1]. - MHC molecules play a central role in the **immune response** by determining the compatibility of tissue transplanted between individuals [1]. *HLA - Antigen* - HLA is a part of the **MHC** and represents a group of genes, but it is not the most crucial factor for initiating graft rejection on its own. - HLA typing is significant for compatibility [2], but the overall process of rejection is driven by **MHC** interactions with T-cells [1]. *DHA* - **DHA** does not relate to graft rejection as it is an **omega-3 fatty acid** rather than an immune antigen. - It has no direct involvement in **immune response** or tissue compatibility processes. *Polysaccharide* - Polysaccharides are primarily components of **cell walls** in bacteria and fungi, and are not involved in the rejection of grafts. - They do not activate **T-cells** or engage in the typical mechanisms of **graft rejection** mediated by MHC. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 239-241. [2] 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. 179-180.

Q: Ram Devi presented with acute onset of generalized edema, sweating, and urticaria within minutes of eating peanuts. This is most suggestive of:

IgE mediated reaction. ***IgE mediated reaction*** - **Generalized edema and sweating** are classic symptoms associated with an IgE mediated hypersensitivity reaction, commonly seen in allergic responses [1][2]. - Often results in **anaphylaxis** or allergic urticaria, which can cause systemic reactions leading to edema [4]. *IgA mediated hypersensitivity reaction* - Primarily involved in **mucosal immunity**; does not typically cause **generalized edema** or sweating. - Conditions like **Celiac disease** may present with gastrointestinal symptoms, not systemic edema. *IgG mediated reaction* - IgG hypersensitivity typically occurs in **delayed-type hypersensitivity** or autoimmune disorders, rather than causing acute systemic symptoms like edema [2]. - Often associated with chronic conditions and would not present with **sweating** as a primary feature. *T cell mediated cytotoxicity* - Involves **CD8+ T cells** targeting and destroying infected or dysfunctional cells; not characterized by **systemic edema** or sweating [3]. - More related to **cell-mediated immunity**, particularly in viral infections or graft rejection, rather than immediate hypersensitivity [3]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 211-212. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-210. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 216-218. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 212-213.

Question 1

Which of the following HLA types is most commonly associated with rheumatoid arthritis?

Accepted Answer

HLA DR4

Answer

HLA DR8

Answer

HLA DQ1

Answer

HLA B27

Question 2

Hypersensitivity pneumonitis is classically an immunologically mediated inflammatory reaction. Which type of hypersensitivity is primarily involved?

Accepted Answer

Type IV hypersensitivity

Answer

Type III hypersensitivity

Answer

Type I hypersensitivity

Answer

Type II hypersensitivity

Question 3

Histamine in anaphylaxis is secreted by which of the following cells?

Accepted Answer

Mast cells

Answer

B-cells

Answer

Basophils

Answer

Macrophages

Question 4

What type of hypersensitivity reaction is primarily associated with allergic rhinitis?

Accepted Answer

Type I hypersensitivity reaction

Answer

Type IV hypersensitivity reaction

Answer

Type II hypersensitivity reaction

Answer

Type III hypersensitivity reaction

Question 5

The hypersensitivity reaction involved in the hyperacute rejection of a renal transplant is:

Accepted Answer

Type II

Answer

Type I

Answer

Type III

Answer

Type IV

Question 6

Delayed hypersensitivity is primarily mediated by:

Accepted Answer

Lymphocytes

Answer

Neutrophils

Answer

Eosinophils

Answer

Monocytes

Question 7

Allograft rejection is an example of which type of hypersensitivity reaction?

Accepted Answer

Type IV hypersensitivity

Answer

Type I hypersensitivity

Answer

Type II hypersensitivity

Answer

Type III hypersensitivity

Question 8

Which type of hypersensitivity reaction is characterized by immune complex formation?

Accepted Answer

Type-III

Answer

Type-I

Answer

Type-II

Answer

Type-IV

Question 9

Which antigen is most critical in initiating graft rejection?

Accepted Answer

HLA - Antigen

Answer

DHA

Answer

Polysaccharide

Answer

MHC - molecule

Question 10

Ram Devi presented with acute onset of generalized edema, sweating, and urticaria within minutes of eating peanuts. This is most suggestive of:

Accepted Answer

IgE mediated reaction

Answer

T cell mediated cytotoxicity

Answer

IgG mediated reaction

Answer

IgA mediated hypersensitivity reaction

Immunopathology — MCQs

Immunopathology — MCQs

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