A patient is suffering from an auto-immune disorder. Exome analysis has revealed a mutation in the gene
‘AIRE’. Which one of the following biological processes is likely to be affected in this patient?
(1) Positive selection of thymocytes
(2) Negative selection of thymocytes
(3) Affinity maturation
(4) Dendritic cell development

📘 Problem Statement

A patient with an autoimmune disorder has undergone exome analysis revealing a mutation in the AIRE gene. Which biological process is likely to be affected in this patient?

Options:

1. Positive selection of thymocytes

• • Positive Selection of Thymocytes: This is the first step in T cell development, occurring in the thymus. Thymocytes that can recognize self-MHC molecules are selected to survive and mature. This process ensures that the T cells are capable of recognizing antigens in the context of the body’s own MHC molecules.

  • Negative Selection of Thymocytes: This second step involves the elimination of thy

  • Negative selection of thymocytes

  • Affinity maturation

  • Dendritic cell development

🔬 The Role of the AIRE Gene in Immune Function

The AIRE (Autoimmune Regulator) gene plays a crucial role in the development of immune tolerance by regulating the negative selection of thymocytes in the thymus. This process is vital in ensuring that T cells that recognize self-antigens are eliminated, thus preventing autoimmune reactions.

Let’s explore what happens in detail and how a mutation in this gene affects thymocyte selection:

🧠 Thymocyte Selection: Positive vs. Negative

• mocytes that bind too strongly to self-antigens presented by self-MHC molecules. The AIRE gene is key here. It ensures that a wide range of tissue-specific self-antigens are presented in the thymus, so thymocytes that react to self-components are deleted. If this process fails due to an AIRE mutation, it can lead to the survival of autoreactive T cells, contributing to autoimmune disorders.

🔬 Impact of AIRE Mutation

A mutation in the AIRE gene primarily disrupts negative selection. In the absence of proper AIRE gene function, thymocytes that strongly react to self-antigens are not eliminated. These self-reactive T cells can survive and enter circulation, where they may attack the body’s own tissues, leading to autoimmunity.

This is why patients with AIRE gene mutations often develop autoimmune conditions, such as autoimmune polyendocrinopathy syndrome (APS-1), which involves multiple organ systems, including the endocrine glands.

✅ The Correct Answer

The biological process most likely to be affected in a patient with a mutation in the AIRE gene is:

2. Negative selection of thymocytes

💡 Key Takeaways

• AIRE gene is essential for negative selection of thymocytes, which eliminates T cells that react to self-antigens.

• A mutation in AIRE impairs this process, leading to autoreactive T cells and autoimmune disorders.

• Autoimmune diseases associated with AIRE mutations include APS-1, which affects the immune system’s tolerance mechanisms.

• Positive selection of thymocytes, affinity maturation, and dendritic cell development are not directly affected by AIRE mutations