T cells

From Canonica AI

Introduction

T cells, also known as T lymphocytes, are a type of white blood cell that play a crucial role in the immune response. They are one of the main components of the adaptive immune system, which provides the body with a tailored defense against specific pathogens. T cells are named after the thymus, an organ situated behind the sternum where they mature.

A close-up microscopic image of a T cell.
A close-up microscopic image of a T cell.

Types of T cells

There are several different types of T cells, each with a unique role in the immune response.

Helper T cells

Helper T cells (Th cells) are the most abundant type of T cell. They are responsible for coordinating the immune response by activating other immune cells, such as B cells and cytotoxic T cells.

Cytotoxic T cells

Cytotoxic T cells (Tc cells) are the primary effector cells of the adaptive immune system. They are capable of directly killing infected cells, as well as cancer cells.

Regulatory T cells

Regulatory T cells (Tregs) play a crucial role in maintaining immune homeostasis by suppressing excessive immune responses that could lead to autoimmunity or tissue damage.

Memory T cells

Memory T cells are a subset of T cells that provide long-lasting immunity by remembering specific pathogens. They can rapidly respond to subsequent encounters with the same pathogen, providing a faster and more effective immune response.

T cell development

T cells originate from hematopoietic stem cells in the bone marrow. These cells migrate to the thymus, where they undergo a complex process of maturation and selection.

Positive selection

Positive selection tests whether T cells can recognize and bind to self-MHC molecules. Only those T cells that can bind to MHC molecules with a certain affinity are allowed to survive.

Negative selection

Negative selection tests whether T cells react against self-antigens. T cells that bind too strongly to self-antigens are eliminated to prevent autoimmunity.

T cell activation

T cell activation occurs when a T cell receptor (TCR) recognizes and binds to a specific antigen presented by an MHC molecule on the surface of an antigen-presenting cell (APC). This triggers a series of intracellular signaling pathways that lead to T cell proliferation and differentiation.

Costimulation

Costimulation is a secondary signal required for full T cell activation. It involves the interaction between costimulatory molecules on the T cell and the APC.

T cell functions

T cells perform a variety of functions in the immune response, including:

  • Direct killing of infected or cancerous cells (cytotoxic T cells)
  • Activation of other immune cells (helper T cells)
  • Suppression of immune responses (regulatory T cells)
  • Memory of past infections (memory T cells)

T cells and disease

T cells are involved in a variety of diseases, including autoimmune diseases, infectious diseases, and cancer.

Autoimmune diseases

In autoimmune diseases, T cells mistakenly recognize self-antigens as foreign and mount an immune response against the body's own tissues. Examples include type 1 diabetes, rheumatoid arthritis, and multiple sclerosis.

Infectious diseases

In infectious diseases, T cells play a crucial role in controlling and eliminating the pathogen. However, some pathogens have evolved strategies to evade T cell responses.

Cancer

In cancer, T cells can recognize and kill cancer cells. However, cancer cells often develop mechanisms to evade T cell recognition or to inhibit T cell function.

T cell therapies

T cell therapies are a promising area of research in the treatment of cancer and other diseases. These therapies involve the manipulation of T cells to enhance their ability to recognize and kill disease cells.

CAR T-cell therapy

CAR T-cell therapy is a type of immunotherapy that involves genetically modifying a patient's own T cells to express a chimeric antigen receptor (CAR) that can recognize a specific antigen on cancer cells.

See Also