Immunopathology Practice Questions

Q: A woman receives an organ transplant from her sister who is an identical twin. What type of graft is it?

Isograft. ***Isograft*** - An isograft (or syngeneic graft) refers to tissue transplanted between **genetically identical** individuals, such as identical twins. - In such cases, there is no **immune rejection** because the donor and recipient share the exact same genetic makeup. *Xenograft* - A xenograft involves transplanting tissue or organs from one **species to another**, for example, from a pig to a human. - These grafts typically face strong and immediate **immune rejection** due to significant genetic differences. *Autograft* - An autograft is a transplant of tissue from one part of an individual's body to **another part of the same individual**. - Examples include a **skin graft** from a thigh to a burn on the arm, and there is no risk of immune rejection. *Allograft* - An allograft involves transplanting tissue or organs between **genetically non-identical individuals of the same species**, such as a transplant from one human to another unrelated human. - These grafts typically require **immunosuppressive drugs** to prevent rejection due to genetic differences.

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: What is a xenograft?

Graft from 1 species to other species. ***Graft from 1 species to other species*** - A **xenograft**, also known as a **heterograft**, is defined as the transplantation of organs or tissues from one species to another. - Examples include using **porcine (pig)** heart valves in human patients or transplanting baboon hearts into human infants, though the latter is rarely done now due to ethical issues and immunological rejection. *Graft from sister to brother* - This describes an **allograft**, also known as a **homograft**, which is a transplant between genetically different individuals of the same species. - While genetically related, a sister and brother are not genetically identical, thus requiring some degree of **immunosuppression** to prevent rejection. *Graft from father to other child* - This is also an **allograft** or **homograft**, as it involves transplantation between genetically distinct individuals of the same species. - The degree of genetic match would be moderate, similar to a sibling transplant but with potentially more **HLA mismatches**. *Graft from 1 twin to other twin* - This is an **isograft**, also known as an **isogenic graft**, and refers to a transplant between genetically identical individuals, such as identical twins. - Such grafts typically do not elicit an immune response, as the donor and recipient share the exact same **MHC (HLA)** antigens.

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.

Q: Onion peel appearance of splenic capsule is seen in

SLE. ### SLE [1] - The **onion peel appearance** of the splenic capsule is a characteristic histological finding in **Systemic Lupus Erythematosus (SLE)**. - It results from **concentric perivascular fibrosis** and **lamellar thickening** around central arterioles in the spleen, a manifestation of autoimmune damage [1]. *Scleroderma* - **Scleroderma** is characterized by excessive **collagen deposition** and fibrosis in tissues, which would not typically manifest as an "onion peel" appearance in the spleen. - While it can affect connective tissue throughout the body, splenic involvement is usually not described with this specific histological finding. *Rheumatoid arthritis* - **Rheumatoid arthritis** primarily affects synovial joints and is associated with **chronic inflammation** and pannus formation. - Splenic changes in RA, if present (e.g., Felty's syndrome), involve splenomegaly due to lymphoid hyperplasia, not concentric perivascular fibrosis. *Sjögren's syndrome* - **Sjögren's syndrome** is an autoimmune disease primarily affecting **exocrine glands**, leading to dry eyes and mouth. - While systemic manifestations can occur, the characteristic "onion peel" splenic changes are not associated with Sjögren's syndrome. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 685-686.

Q: Rheumatoid factor is mainly-

IgM. ***IgM*** - **Rheumatoid factor (RF)** is primarily an **IgM antibody** that targets the Fc portion of human IgG. While other isotypes (IgA, IgG) can also act as RF, the classic laboratory test predominantly detects **IgM-RF**. [2] *IgG* - Although IgG is the target of rheumatoid factor, the rheumatoid factor itself is **not typically an IgG antibody**. [1] - IgG rheumatoid factors do exist but are **less common** than IgM rheumatoid factors and generally not the primary antigen detected in standard RF assays. *IgD* - **IgD antibodies** are found in very small amounts in the serum and their primary role is largely unknown, though they are involved in B cell activation. - IgD is **not a common isotype** for rheumatoid factor and plays a negligible role in its pathogenesis or detection. *IgA* - **IgA rheumatoid factors** can be present in some patients with rheumatoid arthritis, and their presence may correlate with more severe disease. - However, **IgA-RF is less prevalent** than IgM-RF and is not the main type of antibody measured in standard RF tests. **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] 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. 154-155.

Q: Transplantation between identical twins-

Isograft. ***Isograft*** - An **isograft** refers to a transplant between **genetically identical individuals**, such as identical twins, thus minimizing immune rejection [1]. - Due to the identical genetic makeup, the recipient's immune system will not recognize the transplanted tissue as foreign, making **immunosuppression unnecessary** [1]. *Xenograft* - A **xenograft** involves transplantation of tissues or organs between **different species**, for example, from a pig to a human. - These grafts typically face severe and rapid **immune rejection** due to significant genetic differences between the donor and recipient species. *Autograft* - An **autograft** is a transplant of tissue from **one part of an individual's body to another part of the same individual**. - This type of graft has no risk of rejection as the tissue is genetically identical to the recipient's own tissue [2]. *Allograft* - An **allograft** is a transplant between **genetically non-identical individuals of the same species**, such as between two non-twin humans. - These grafts always require **immunosuppressive therapy** to prevent rejection due to genetic differences, though rejection rates vary based on HLA matching [1].

Question 1

A woman receives an organ transplant from her sister who is an identical twin. What type of graft is it?

Accepted Answer

Isograft

Answer

Xenograft

Answer

Autograft

Answer

Allograft

Question 2

A 32 year old man presents with a 3-month history of weight loss, night sweats, a productive cough with blood-tinged sputum, anorexia, general malaise, and a low grade fever. A PPD skin test shows > 10 mm of induration. If the area of induration were biopsied, which of the following type of reactive cells would be found?

Accepted Answer

T lymphocyte

Answer

Eosinophil

Answer

B lymphocyte

Answer

Mast cell

Question 3

HLA associated with Rheumatoid arthritis is?

Accepted Answer

HLA-DR4

Answer

HLA-Cw6

Answer

HLA-B8

Answer

HLA-B27

Question 4

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 5

What is a xenograft?

Accepted Answer

Graft from 1 species to other species

Answer

Graft from sister to brother

Answer

Graft from father to other child

Answer

Graft from 1 twin to other twin

Question 6

Rheumatoid factor is directed against ?

Accepted Answer

IgG

Answer

IgA

Answer

IgM

Answer

IgD

Question 7

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

Question 8

Onion peel appearance of splenic capsule is seen in

Accepted Answer

SLE

Answer

Scleroderma

Answer

Rheumatoid arthritis

Answer

Sjögren's syndrome

Question 9

Rheumatoid factor is mainly-

Accepted Answer

IgM

Answer

IgG

Answer

IgD

Answer

IgA

Question 10

Transplantation between identical twins-

Accepted Answer

Isograft

Answer

Xenograft

Answer

Autograft

Answer

Allograft

Immunopathology — MCQs

Immunopathology — MCQs

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