T cell activation

Definition

T cell activation is the process by which naive T cells become fully functional immune cells capable of responding to pathogens. This process involves the recognition of specific antigens presented by antigen-presenting cells (APCs) and subsequent signaling events that lead to T cell proliferation, differentiation, and effector function. Proper T cell activation is crucial for mounting an effective immune response and plays a significant role in immunotherapy strategies against cancer.

5 Must Know Facts For Your Next Test

1. T cell activation requires two main signals: recognition of a specific antigen by the T cell receptor (TCR) and a second signal from co-stimulatory molecules on APCs.
2. Naive T cells differentiate into various subtypes, such as helper T cells or cytotoxic T cells, based on the cytokine environment during activation.
3. The duration and strength of T cell activation can influence the outcome of immune responses, with stronger activation leading to more robust effector functions.
4. Immunotherapies often target T cell activation pathways to enhance anti-tumor responses, with strategies like CAR T-cell therapy being examples of this approach.
5. Failure of T cell activation can lead to immune evasion by cancer cells, underscoring the importance of this process in cancer immunotherapy.

Review Questions

• Explain the two main signals required for T cell activation and their significance in the immune response.
  • T cell activation requires two essential signals: the first is the recognition of a specific antigen by the T cell receptor (TCR), which is presented by antigen-presenting cells (APCs). The second signal comes from co-stimulatory molecules on the surface of APCs interacting with receptors on T cells. Both signals are crucial for full T cell activation; without them, naive T cells may become anergic or fail to mount an effective immune response.
• Discuss how cytokines influence the differentiation of activated T cells into various subtypes and their roles in the immune system.
  • Cytokines play a pivotal role in guiding the differentiation of activated T cells into specific subtypes like helper T cells (Th1, Th2) or cytotoxic T lymphocytes (CTLs). The type of cytokines present during T cell activation influences whether a naive CD4+ T cell will become a Th1 cell, promoting cellular immunity, or a Th2 cell, which helps in antibody production. This differentiation is vital for tailoring the immune response to effectively target different pathogens or tumor cells.
• Analyze the impact of checkpoint inhibitors on T cell activation and their role in enhancing anti-tumor immunity.
  • Checkpoint inhibitors are therapeutic agents designed to block inhibitory signals that dampen T cell activation, thereby enhancing anti-tumor immunity. By inhibiting proteins such as PD-1 or CTLA-4 on T cells, these drugs remove the brakes on the immune system, allowing activated T cells to proliferate and effectively attack cancer cells. This strategy has revolutionized cancer treatment by improving the ability of T cells to recognize and eliminate tumors, demonstrating how manipulating T cell activation can lead to significant clinical benefits.

Related terms

Antigen-presenting cells (APCs): Cells that process and present antigens to T cells, including dendritic cells, macrophages, and B cells, playing a key role in initiating T cell activation.

Cytokines:

Signaling molecules secreted by immune cells that influence the activation, growth, and differentiation of T cells and other immune responses.

Checkpoint inhibitors: Therapeutic agents that block proteins that inhibit T cell activation, enhancing the immune response against cancer cells.