U01.02.014 Regulatory T cells

Regulatory T cells (Tregs) are a subset of T cells crucial for maintaining immune homeostasis and preventing autoimmune diseases. They function by modulating the immune response, especially suppressing the activity of effector T cells.

Characteristics of Regulatory T Cells

Immune Tolerance: Tregs help maintain specific immune tolerance by suppressing the effector functions of CD4+ and CD8+ T cells. This prevents excessive immune reactions.
Markers: Identified by the expression of specific surface markers, including:
- CD3: T-cell receptor component
- CD4: Helper T-cell marker
- CD25: High-affinity IL-2 receptor alpha chain
- FOXP3: Master regulator transcription factor for Treg development and function
Anti-inflammatory Cytokines: Once activated, Tregs secrete key anti-inflammatory cytokines such as:
- IL-10
- TGF-β (Transforming Growth Factor-beta)

Role of Regulatory T Cells

Function	Description
Immune Suppression	Suppress CD4+ and CD8+ T cell effector functions to prevent autoimmunity.
Cytokine Production	Produce anti-inflammatory cytokines like IL-10 and TGF-β to modulate immune response.
Maintain Immune Homeostasis	Help regulate the immune system to prevent overactive responses.

Role of Regulatory T Cells

IPEX Syndrome (Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-linked)

Overview

IPEX syndrome is a rare genetic disorder caused by a deficiency in the FOXP3 gene, leading to dysfunctional regulatory T cells and a loss of immune tolerance. This results in autoimmune diseases affecting multiple organ systems.

Clinical Features

Autoimmune Enteropathy: Inflammation of the intestines leading to diarrhea and malabsorption.
Endocrinopathies: Disorders of the endocrine glands, such as Type 1 diabetes.
Nail Dystrophy: Abnormal growth and appearance of nails.
Dermatitis: Chronic skin inflammation with potential for autoimmune involvement.
Other Autoimmune Conditions: These can include additional dermatological or systemic autoimmune disorders.

Feature	Description
Genetic Cause	FOXP3 gene mutation (X-linked inheritance).
Symptoms	Enteropathy, endocrinopathy, nail dystrophy, dermatitis.
Diabetes in Male Infants	Strong association with diabetes mellitus in affected males.

Points to Remember

Regulatory T cells (Tregs) are essential for preventing autoimmune diseases by suppressing overactive immune responses.
They are characterized by the expression of CD3, CD4, CD25, and FOXP3.
FOXP3 deficiency leads to IPEX syndrome, a rare disorder with systemic autoimmune manifestations.
Tregs produce key anti-inflammatory cytokines like IL-10 and TGF-β.

Bibliography

Sakaguchi, S., et al. “Regulatory T Cells: How Do They Suppress Immune Responses?” Nature Reviews Immunology, vol. 8, no. 5, 2008, pp. 345-357.
Wildin, R. S., et al. “IPEX, FOXP3, and the Role of Regulatory T Cells in Autoimmune Diseases.” The Journal of Clinical Investigation, vol. 112, no. 9, 2003, pp. 1237-1242.
Bennett, C. L., et al. “The Immune Dysregulation Polyendocrinopathy Enteropathy X-Linked Syndrome (IPEX) and FOXP3.” Nature Genetics, vol. 27, 2001, pp. 20-21.

USMLE Step 1 Review Series

Curriculum

U01.02.014 Regulatory T cells

Characteristics of Regulatory T Cells

Role of Regulatory T Cells

IPEX Syndrome (Immune Dysregulation, Polyendocrinopathy, Enteropathy, X-linked)

Overview

Clinical Features

Points to Remember

Bibliography

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