Cytotoxic T-lymphocyte activator

T-cell activation

This page provides an overview of T-cell activation, a critical process in the adaptive immune response.

Introduction to T-cell Activation

T-cells are a type of lymphocyte that play a central role in cell-mediated immunity. Their activation is a tightly regulated process essential for mounting an effective immune response against pathogens and abnormal cells.

Key Steps in T-cell Activation

The activation of naive T-cells requires two primary signals presented by antigen-presenting cells (APCs).

Signal 1: Antigen Recognition

The T-cell receptor (TCR) binds to a specific peptide antigen presented on the major histocompatibility complex (MHC) molecule on the APC.

Signal 2: Co-stimulation

Binding of co-stimulatory molecules on the APC (e.g., B7) to their receptors on the T-cell (e.g., CD28) provides a necessary second signal for full activation.

Outcomes of Activation

Upon receiving both signals, the T-cell undergoes clonal expansion and differentiation into effector cells.

Effector T-cell Types

• Cytotoxic T-cells (CD8+): Directly kill infected or cancerous cells.
• Helper T-cells (CD4+): Secrete cytokines to help activate other immune cells like B-cells and macrophages.
• Regulatory T-cells (Tregs): Suppress immune responses to maintain tolerance and prevent autoimmunity.

Importance in Health and Disease

Proper T-cell activation is crucial for vaccine efficacy and fighting infections. Dysregulation can lead to immunodeficiency, autoimmunity, or cancer.