Immunopathology Practice Questions

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: What is the definitive method for identifying amyloid deposits?

Congo red staining with polarized light microscopy. ***Green birefringence of stained amyloid when viewed by polarizing microscope*** - When stained with **Congo red**, amyloid exhibits **green birefringence** when viewed under polarized light, which is a hallmark for its identification [1]. - This characteristic is crucial for confirming the presence of amyloid deposits in tissues during histopathological examination [1]. *Secondary fluorescence in UV light with riboflavin* - This method is not a recognized technique for identifying amyloid, as it primarily deals with **fluorescent properties** not linked to amyloid detection. - **Riboflavin** itself is not associated with amyloid identification and does not indicate its presence in tissues. *Congo red* - While **Congo red** is a staining method for detecting amyloid, it needs to be combined with a polarizing microscope to visualize the characteristic **birefringence** [1]. - Simply using Congo red does not provide the definitive identification without considering its polarization properties [1]. *Staining with methyl violet* - **Methyl violet** is used for various histological stains but does not specifically identify amyloid deposits. - This method lacks the specificity needed for detecting amyloid, making it unsuitable compared to other recognized techniques. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 268-269.

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.

Q: The type of allergic reaction seen in allergic fungal sinusitis is -

Type 1 and Type 3. ***Type 1 and Type 3*** - **Allergic fungal sinusitis (AFS)** is primarily characterized by **IgE-mediated hypersensitivity (Type I)** against fungal antigens, manifesting as immediate allergic responses [1]. - **Immune complex formation and deposition (Type III hypersensitivity)** also plays a significant role, contributing to chronic inflammation and tissue damage in the sinuses [2]. - These are considered the **predominant mechanisms** in AFS pathogenesis for clinical and examination purposes. *Type 1 and Type 2* - While **Type I hypersensitivity** (IgE-mediated) is a key component of AFS, **Type II hypersensitivity** (cytotoxic, antibody-dependent) is not involved [1]. - Type II reactions involve antibodies binding to cell surface antigens causing direct cell destruction, which is not a mechanism in AFS [1]. *Type 2 and Type 3* - **Type II hypersensitivity** is not a mechanism in AFS, as the disease does not involve antibody-mediated cellular cytotoxicity [1]. - Although **Type III hypersensitivity** is involved, the absence of Type I (the primary mechanism) makes this option incorrect [2]. *Type 4 and Type 1* - **Type I hypersensitivity** is the primary mechanism in AFS [1]. **Type IV hypersensitivity** (delayed-type, T-cell mediated) may play a contributory role in chronic inflammation. - However, the **classic teaching emphasizes Types I and III** as the predominant hypersensitivity reactions in AFS, with Type I (IgE-mediated) and Type III (immune complex) being the primary drivers of the clinical presentation and pathology [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 208-211. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 214-215.

Question 1

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 2

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

Accepted Answer

Mast cells

Answer

B-cells

Answer

Basophils

Answer

Macrophages

Question 3

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 4

Delayed hypersensitivity is primarily mediated by:

Accepted Answer

Lymphocytes

Answer

Neutrophils

Answer

Eosinophils

Answer

Monocytes

Question 5

What is the definitive method for identifying amyloid deposits?

Accepted Answer

Congo red staining with polarized light microscopy

Answer

Thioflavin T fluorescence microscopy

Answer

Methyl violet staining

Answer

Riboflavin fluorescence under UV light

Question 6

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 7

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 8

Which antigen is most critical in initiating graft rejection?

Accepted Answer

HLA - Antigen

Answer

DHA

Answer

Polysaccharide

Answer

MHC - molecule

Question 9

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

Question 10

The type of allergic reaction seen in allergic fungal sinusitis is -

Accepted Answer

Type 1 and Type 3

Answer

Type 2 and Type 3

Answer

Type 1 and Type 2

Answer

Type 4 and Type 1

Immunopathology — MCQs

Immunopathology — MCQs

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