Immunopathology Practice Questions

Q: Which of the following types of hypersensitivity reactions is associated with the given condition?

Cytotoxic type. ***Cytotoxic type*** - **Type II hypersensitivity** involves **IgG/IgM antibodies** binding to cell-surface or extracellular matrix antigens, leading to **complement activation** and **cell destruction**. - Classic example is **pemphigus vulgaris** where antibodies target **desmoglein proteins** in desmosomes, causing **acantholysis** and blister formation. *Anaphylactic type* - **Type I hypersensitivity** is mediated by **IgE antibodies** and **mast cell degranulation**, causing immediate reactions like **anaphylaxis**. - Involves **histamine release** and **vasodilation**, not direct cellular destruction by antibodies against structural proteins. *Type III hypersensitivity* - **Immune complex-mediated** reaction involving **antigen-antibody complexes** depositing in tissues, causing **inflammation**. - Examples include **serum sickness** and **lupus nephritis**, not autoantibodies targeting specific cell adhesion molecules. *Cell-mediated hypersensitivity* - **Type IV hypersensitivity** involves **T-cells** and **delayed-type reactions**, typically occurring **48-72 hours** after exposure. - Examples include **contact dermatitis** and **tuberculin skin test**, not antibody-mediated cellular damage.

Q: T cells recognize which antigen during graft rejection?

Both MHC I and MHC II. **Explanation:** Graft rejection is primarily a **cell-mediated immune response** driven by the recognition of non-self **Major Histocompatibility Complex (MHC)** molecules, also known as Human Leukocyte Antigens (HLA) in humans. **Why the correct answer is C:** Graft rejection involves the activation of two main subsets of T cells: 1. **CD8+ Cytotoxic T cells:** These recognize **MHC Class I** molecules (HLA-A, B, C) present on all nucleated cells of the graft. Once activated, they cause direct lysis of the graft tissue. 2. **CD4+ Helper T cells:** These recognize **MHC Class II** molecules (HLA-DR, DQ, DP) present on professional antigen-presenting cells (APCs) within the graft (Direct pathway) or host APCs that have processed graft antigens (Indirect pathway). CD4+ cells are crucial for secreting cytokines that recruit macrophages and provide "help" to B cells and CD8+ cells. Since both CD4+ and CD8+ pathways are essential for the full spectrum of rejection, T cells must recognize both MHC I and MHC II. **Why other options are incorrect:** * **Option A & B:** These are incomplete. While CD4+ cells recognize MHC II and CD8+ cells recognize MHC I, the process of rejection is a coordinated effort involving both cell types. Selecting only one ignores the fundamental synergy required for an immune response against a vascularized organ. **High-Yield Clinical Pearls for NEET-PG:** * **Direct Pathway:** Recipient T cells recognize intact donor MHC on donor APCs (important in acute rejection). * **Indirect Pathway:** Recipient APCs process donor MHC and present it to recipient T cells (important in chronic rejection). * **Hyperacute Rejection:** Occurs within minutes; mediated by **preformed antibodies**, not T cells. * **MHC Restriction:** Remember the "Rule of 8": CD4 × MHC II = 8; CD8 × MHC I = 8.

Question 1

MALT is most commonly present in which part of the small intestine?

Accepted Answer

Ileum

Answer

Duodenum

Answer

Jejunum

Answer

Stomach

Question 2

Which of the following types of hypersensitivity reactions is associated with the given condition?

Accepted Answer

Cytotoxic type

Answer

Anaphylactic type

Answer

Type III hypersensitivity

Answer

Cell-mediated hypersensitivity

Question 3

Which of the following organs is NOT typically affected in Graft-Versus-Host disease?

Accepted Answer

Lung

Answer

Skin

Answer

Gastrointestinal tract

Answer

Liver

Question 4

The interaction of antigens with antibodies on the surface of a mast cell leads to degranulation and anaphylaxis. The mast cell granules produce anaphylaxis because they contain:

Accepted Answer

Vasoactive mediators

Answer

Lysosomes

Answer

Proteolytic enzymes

Answer

Lymphotoxins

Question 5

T cells recognize which antigen during graft rejection?

Accepted Answer

Both MHC I and MHC II

Answer

MHC II

Answer

MHC I

Answer

None

Question 6

Which of the following interleukins is characteristically produced in a TH1 response?

Accepted Answer

IL-2

Answer

IL-4

Answer

IL-5

Answer

IL-10

Question 7

What is a common consequence of hypogammaglobulinemia?

Accepted Answer

Chronic recurrent sinusitis

Answer

Epistaxis

Answer

Contractures

Answer

Eczema

Question 8

Allograft rejection is an example of which type of immune response?

Accepted Answer

Delayed-type hypersensitivity

Answer

Graft-versus-host disease (GVHD)

Answer

Immediate hypersensitivity

Answer

Acute rejection

Question 9

All are true about severe combined immunodeficiency except?

Accepted Answer

Affected child can survive beyond adolescence without treatment

Answer

B and T cell deficiency

Answer

Adenosine deaminase deficiency may occur

Answer

Can transmit either as X-linked or autosomal recessive defect

Question 10

A 63-year-old man presents with a 15-year history of chronic arthritis. Physical examination reveals ulnar deviation, bony ankylosis, and swan neck deformities of the fingers. Laboratory findings include 4.2 g of protein in a 24-hour urine collection, a serum creatinine of 3.1 mg/dL, and blood urea nitrogen of 30 mg/dL. The C-reactive protein level is markedly elevated. A rectal biopsy shows amorphous pink material deposited in the mucosa, which stains positive with Congo red on H&E staining. Which of the following proteins is the most likely precursor to this material in the mucosa?

Accepted Answer

Acute-phase reactant

Answer

beta2-Microglobulin

Answer

gamma light chains

Answer

Transthyretin

Immunopathology — MCQs

Immunopathology — MCQs

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