Immunopathology Practice Questions

Q: The primary defect in chronic granulomatous disease (CGD) is:

Defective H2O2 production. ***Defective H2O2 production*** - Chronic granulomatous disease (CGD) is a primary immunodeficiency characterized by the inability of phagocytes (neutrophils, macrophages) to produce **reactive oxygen species**, specifically **superoxide** and its derivatives like H2O2. - This defect is primarily due to mutations in genes encoding components of the **NADPH oxidase enzyme complex**, which is crucial for the **oxidative burst** leading to H2O2 and other antimicrobial agents. *Defective phagocytosis* - Defective phagocytosis refers to an impairment in the engulfment of pathogens, which is not the primary defect in CGD. - In CGD, phagocytes can engulf pathogens, but they cannot effectively kill them intracellularly due to the lack of an **oxidative burst**. *Job's disease* - Job's disease, also known as **hyper-IgE syndrome**, is characterized by high IgE levels, recurrent skin and pulmonary infections, and distinctive facial features. - It is caused by genetic defects in the **STAT3 pathway**, which affects immune cell differentiation and function, and does not involve a primary defect in H2O2 production. *Myeloperoxidase deficiency* - Myeloperoxidase (MPO) deficiency is a condition where neutrophils lack the enzyme **myeloperoxidase**, which contributes to the formation of hypochlorous acid (HOCl) from H2O2 and chloride ions. - While MPO is involved in microbial killing, its deficiency is generally less severe than CGD, as other mechanisms (like H2O2 itself) can still kill pathogens; CGD has a more profound defect in the initial production of ROS.

Q: Onion skin spleen is seen in:

SLE. ***SLE*** - **Onion skin spleen** is a characteristic pathological finding in **Systemic Lupus Erythematosus (SLE)**, representing concentric perivascular fibrosis in the splenic arterioles. - This fibrosis is thought to be due to immune complex deposition and chronic inflammation around blood vessels. *ITP* - **Idiopathic Thrombocytopenic Purpura (ITP)** is characterized by **immune-mediated destruction of platelets**, leading to low platelet counts. - While the spleen is involved in platelet destruction in ITP, it does not typically show the "onion skin" appearance; its pathology is usually normal or shows only signs of increased platelet phagocytosis. *Thalassemia* - **Thalassemia** is a group of inherited blood disorders characterized by **reduced or absent synthesis of globin chains**, leading to ineffective erythropoiesis and chronic hemolysis. - The spleen in thalassemia often shows **extramedullary hematopoiesis** and **splenomegaly** due to increased destruction of abnormal red blood cells, but not onion skin fibrosis. *Scleroderma* - **Scleroderma**, or Systemic Sclerosis, is a **chronic autoimmune connective tissue disease** characterized by fibrosis of the skin and internal organs. - While scleroderma can affect various organs, **splenic involvement with onion skin fibrosis is not a typical feature**; its pathology often involves vascular changes and fibrosis in affected tissues, but not this concentric perivascular pattern in the spleen.

Q: Which cells are responsible for GVHD?

Immunocompetent T cell donor. ***Immunocompetent T cell donor*** - **Graft-versus-host disease (GVHD)** primarily involves **donor T cells** recognizing the recipient's tissues as foreign. - These donor T cells then mount an immune response against the **host's antigens**, leading to tissue damage. *Immunocompetent B cell recipient* - **B cells** are mostly responsible for **humoral immunity** (antibody production), which is not the primary mechanism of GVHD. - While recipient B cells can contribute to immune responses, they are not the main effector cells in initiating and perpetuating GVHD. *Immunocompetent NK cell recipient* - **Natural killer (NK) cells** are part of the innate immune system and can kill target cells without prior sensitization. - However, recipient NK cells are typically suppressed in the transplant setting and do not mediate GVHD; rather, **donor NK cells** can sometimes have a protective role. *Immunocompetent T cell recipient* - The recipient's immune system, including **recipient T cells**, is usually **immunosuppressed** or ablated before transplantation to prevent graft rejection. - If the recipient's T cells were immunocompetent, they would likely reject the graft, leading to **graft rejection (host-versus-graft reaction)**, which is the opposite of GVHD.

Q: All are true for transplanted kidney except which of the following?

HLA identity similarity seen in 1:100 people. ***HLA identity similarity seen in 1:100 people*** - The **HLA (Human Leukocyte Antigen)** system is crucial for compatibility in organ transplantation; the likelihood of finding a suitable match is low [1]. - **HLA matching** significantly impacts transplant success and rejection rates, making this statement incorrect in context to what is true for transplanted kidneys [1]. *CMI is responsible for rejection* - While **cell-mediated immunity (CMI)** plays a role in rejection, it is not the only factor; humoral mechanisms also contribute significantly [1]. - This statement oversimplifies the rejection process, which can involve various **immune responses** [1]. *Previous blood transfusion* - **Previous blood transfusions** can lead to sensitization against donor antigens but do not universally apply to all transplant scenarios. - The relevance of prior transfusions varies based on patient history and the specific organ transplanted, making this statement too general. *Humoral antibody responsible for rejection* - **Humoral rejection** involves antibodies but is not exclusively responsible for all types of rejection, as T-cell mediated (CMI) responses also play a role [1]. - It is not accurate to state that humoral antibodies are the sole factor in transplant rejection [1]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 239-243.

Q: Which condition is not associated with complement deficiency?

Membranous nephritis. Membranous nephritis - Membranous nephritis is associated with immune complex deposition rather than complement deficiencies. [1] - The disease is characterized by thickening of the glomerular basement membrane without significant complement involvement. [1] PNH - Paroxysmal nocturnal hemoglobinuria (PNH) is due to a defect in the GPI-anchor leading to complement-mediated hemolysis. - Complement activation plays a critical role in the destruction of red blood cells in this condition. Hereditary angioedema - Hereditary angioedema is caused by deficiencies in C1 inhibitor, leading to uncontrolled activation of complement. - This results in edema episodes, directly linked to complement pathway dysregulation. SLE - Systemic lupus erythematosus (SLE) involves complement consumption due to autoantibody formation against nuclear antigens. - The disease often presents with hypocomplementemia, indicating complement system involvement.

Q: What is the initial event in serum sickness?

It occurs due to exposure to heterologous antigens.. ***Can lead to leukocytoclastic vasculitis*** - Serum sickness is characterized by the formation of **immune complexes**, which can trigger **leukocytoclastic vasculitis** affecting the blood vessels [1][2]. - Symptoms can include **rash, fever, and arthralgia**, typically occurring 1-3 weeks after exposure to the offending antigen [2]. *Can occur due to homologous antigen* - Serum sickness is usually a reaction to **heterologous** antigens, such as those from animal serum, not **homologous** ones. - Homologous antigens do not typically elicit the immune response seen in serum sickness; hence, this statement is incorrect. *Type 2 hypersensitivity* - Serum sickness is classified as a **Type III hypersensitivity** reaction due to the immune complex formation, not Type II [1]. - Type II is characterized by antibody-mediated destruction of **target cells**, which does not apply here. *Hypercomplementemia* - Serum sickness is associated with **hypocomplementemia** due to complement consumption from immune complex formation, not hypercomplementemia. - This can lead to **decreased complement levels** during the response, making this statement incorrect. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 214-216. [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. 172-173.

Q: What is the number of antigens typically evaluated in comprehensive HLA matching for organ transplantation?

10. ***10*** - The **number of criteria for HLA matching** in organ transplantation is typically 10, consisting of 6 class I and 4 class II antigens. - Proper HLA matching is critical for minimizing the risk of **graft rejection** and ensuring **recipient compatibility** [1]. *16* - While there are various HLA antigens, a total of **16** criteria is not a standard number used for matching purposes. - This number may include other factors but does not represent the core criteria for **HLA matching**. *4* - HLA matching involves more than **4 criteria**, inadequate for reliable transplantation outcomes. - This number does not encompass the essential **class I and class II antigens** that are necessary for effective matching. *22* - A total of **22 criteria** exceeds the conventional standard for HLA matching, which is not practical or necessary. - This figure may relate to overall HLA typing but is not applicable for the matching process itself. **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. 179-180.

Q: What is the most common type of graft rejection?

Acute. ***Acute*** - **Acute rejection** is the most common type of graft rejection, occurring in **10-40% of transplant recipients**. [1] - It typically occurs **days to weeks to months** after transplantation (most commonly within the first 6 months). [1] - Mediated primarily by **T-lymphocytes** (cellular rejection) or **antibodies** (antibody-mediated rejection) reacting against donor antigens. [1] - Usually **responsive to immunosuppressive therapy** when detected early. *Hyperacute* - **Hyperacute rejection** is rare (occurs in <1% of cases) due to routine **pre-transplant cross-matching**. - Occurs within **minutes to hours** after transplantation due to **pre-existing circulating antibodies** against donor antigens. [1] - Results in immediate thrombosis and graft necrosis, requiring **immediate graft removal**. [1] *Chronic* - **Chronic rejection** (chronic allograft dysfunction) develops **months to years** after transplantation. - It is the **most common cause of late graft failure**, but not the most common type of rejection episode. - Characterized by **gradual, progressive loss of graft function** with vascular and fibrotic changes. - **Largely irreversible** and poorly responsive to treatment. *Acute on chronic* - This is **not a primary category** of graft rejection but represents an **acute rejection episode superimposed** on a graft already undergoing chronic changes. - Reflects exacerbation in a chronically rejecting graft. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 239-242.

Q: Post-streptococcal glomerulonephritis (PSGN) is an example of which type of hypersensitivity?

Type -3 hypersensitivity. ***Type -3 hypersensitivity*** - Post-streptococcal glomerulonephritis (PSGN) is caused by **immune complex deposition**, a hallmark of type III hypersensitivity reactions [1][2][3]. - It involves the formation of **antigen-antibody complexes** following a streptococcal infection, leading to inflammation in the kidneys [1][2]. *Type -1 hypersensitivity* - Characterized by **IgE-mediated** reactions, such as allergies and anaphylaxis, which do not apply to PSGN. - It typically involves **mast cells** and histamine release, notably absent in PSGN cases. *Type -4 hypersensitivity* - Involves **T-cell mediated** responses and is related to delayed-type reactions, not applicable to PSGN. - Common examples include **contact dermatitis** and graft-versus-host disease, differing fundamentally from PSGN's mechanism. *Type -2 hypersensitivity* - Characterized by **antibody-mediated cytotoxicity**, such as in hemolytic anemia, unrelated to immune complexes in PSGN. - Typically involves direct damage to cells, contrasting with the immune complex mechanism observed in PSGN [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 Kidney, pp. 910-915. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 215-216.

Question 1

The primary defect in chronic granulomatous disease (CGD) is:

Accepted Answer

Defective H2O2 production

Answer

Job's disease

Answer

Defective phagocytosis

Answer

Myeloperoxidase deficiency

Question 2

Onion skin spleen is seen in:

Accepted Answer

SLE

Answer

ITP

Answer

Thalassemia

Answer

Scleroderma

Question 3

Which cells are responsible for GVHD?

Accepted Answer

Immunocompetent T cell donor

Answer

Immunocompetent NK cell recipient

Answer

Immunocompetent B cell recipient

Answer

Immunocompetent T cell recipient

Question 4

Which type of hypersensitivity is characteristically associated with atopic conditions?

Accepted Answer

Local type I hypersensitivity (e.g., allergic rhinitis, eczema)

Answer

Local type II hypersensitivity (e.g., Goodpasture syndrome)

Answer

Systemic type II hypersensitivity (e.g., autoimmune hemolytic anemia)

Answer

Systemic type I hypersensitivity (e.g., anaphylaxis)

Question 5

All are true for transplanted kidney except which of the following?

Accepted Answer

HLA identity similarity seen in 1:100 people

Answer

Humoral antibody responsible for rejection

Answer

Previous blood transfusion

Answer

CMI is responsible for rejection

Question 6

Which condition is not associated with complement deficiency?

Accepted Answer

Membranous nephritis

Answer

SLE

Answer

PNH

Answer

Hereditary angioedema

Question 7

What is the initial event in serum sickness?

Accepted Answer

It occurs due to exposure to heterologous antigens.

Answer

It is associated with hypocomplementemia.

Answer

It is a type III hypersensitivity reaction.

Answer

It can lead to leukocytoclastic vasculitis.

Question 8

What is the number of antigens typically evaluated in comprehensive HLA matching for organ transplantation?

Accepted Answer

10

Answer

4

Answer

16

Answer

22

Question 9

What is the most common type of graft rejection?

Accepted Answer

Acute

Answer

Hyperacute

Answer

Chronic

Answer

Acute on chronic

Question 10

Post-streptococcal glomerulonephritis (PSGN) is an example of which type of hypersensitivity?

Accepted Answer

Type -3 hypersensitivity

Answer

Type -1 hypersensitivity

Answer

Type -2 hypersensitivity

Answer

Type -4 hypersensitivity

Immunopathology — MCQs

Immunopathology — MCQs

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