Question 1

T cells are exclusively involved in attacking foreign pathogens or virally infected cells.

Accepted Answer

A specific subset called Regulatory T cells (Tregs) actively suppress the immune response and prevent other T cells from attacking healthy host tissues.

Question 2

The body prevents autoimmunity only by destroying bad immune cells before they mature in the thymus.

Accepted Answer

Self-reactive immune cells frequently escape the thymus, but peripheral tolerance via Tregs keeps them in check in the bloodstream and tissues.

Question 3

Consider the following statements regarding Regulatory T cells (Tregs) and peripheral immune tolerance: 1. Shimon Sakaguchi discovered that Tregs actively suppress the immune system to prevent autoimmune diseases. 2. The FOXP3 gene acts as the master transcription factor for the development of regulatory T cells. 3. Central immune tolerance occurs in the peripheral blood, whereas peripheral tolerance occurs in the thymus. How many of the above statements are correct?

Accepted Answer

(b) Only two — Statements 1 and 2 are correct. Sakaguchi discovered Tregs, and Brunkow/Ramsdell linked them to the FOXP3 gene. Statement 3 is incorrect because it swaps the definitions: central tolerance occurs in primary lymphoid organs like the thymus (deleting self-reactive cells), while peripheral tolerance occurs in the peripheral tissues and blood (mediated by Tregs).

Question 4

Match the following terms related to the 2025 Nobel Prize in Medicine with their descriptions: List I: A. FOXP3, B. IPEX Syndrome, C. Central Tolerance, D. Scurfy mice. List II: 1. Elimination of self-reactive T cells in the thymus, 2. Animal model with a fatal autoimmune defect, 3. Human autoimmune disease caused by a specific gene mutation, 4. Transcription factor essential for Regulatory T cell development.

Accepted Answer

(a) A-4, B-3, C-1, D-2 — FOXP3 (A) is the transcription factor gene essential for Tregs (4). IPEX Syndrome (B) is the human autoimmune disease caused by a FOXP3 mutation (3). Central Tolerance (C) is the elimination of self-reactive cells in the thymus (1). Scurfy mice (D) are the historical animal models showing the fatal autoimmune defect used by Brunkow and Ramsdell (2).

Question 5

Assertion (A): Mutations in the human FOXP3 gene lead to the severe autoimmune disorder known as IPEX syndrome. Reason (R): The FOXP3 gene encodes a transcription factor that programs T-cells to become Cytotoxic T-cells, which destroy self-tissues. Select the correct answer.

Accepted Answer

(c) A is correct but R is incorrect — Assertion (A) is true; mutations in FOXP3 cause IPEX syndrome. Reason (R) is false because FOXP3 programs T-cells to become Regulatory T-cells (Tregs) that SUPPRESS the immune response, not Cytotoxic T-cells. The lack of these Tregs due to the mutation is what allows other immune cells to run rampant and destroy self-tissues.

2025 Nobel Prize in Physiology or Medicine Awarded

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