T cells are responsible for coordinating and executing cell-mediated immune responses, which involve the direct killing of infected or cancerous cells and the regulation of other immune cells.

Cytotoxic T cells, also known as killer T cells, are responsible for recognizing and eliminating infected cells or cancerous cells by releasing cytotoxic molecules that induce cell death.

Helper T cells play a crucial role in coordinating immune responses by releasing cytokines that activate other immune cells, such as cytotoxic T cells, B cells, and macrophages.

Regulatory T cells play a critical role in maintaining immune tolerance and preventing excessive immune responses. They suppress the activity of other immune cells to prevent autoimmune reactions and excessive inflammation.

T cell activation is a complex process that involves antigen presentation by antigen-presenting cells (APCs), cytokine signaling, and cell-cell contact between T cells and APCs.

Antigens are presented to T cells by MHC (major histocompatibility complex) molecules. MHC class I molecules present antigens to CD8+ T cells, while MHC class II molecules present antigens to CD4+ T cells.

The TCR is responsible for recognizing antigens presented by MHC molecules, binding to them, and transducing signals into the T cell, leading to its activation.

CD4+ Helper T cells can be divided into two main subsets: Th1 cells and Th2 cells. Th1 cells are involved in cell-mediated immunity, while Th2 cells are involved in humoral immunity.

Th1 cells play a crucial role in cell-mediated immunity by releasing cytokines that activate macrophages and other phagocytic cells, enhancing their ability to kill intracellular pathogens.

Th2 cells play a critical role in humoral immunity by releasing cytokines that stimulate B cells to differentiate into antibody-producing plasma cells, leading to the production of antibodies against pathogens.

Th17 cells are involved in promoting inflammation and immune responses against extracellular bacteria and fungi. They release cytokines that recruit neutrophils and other inflammatory cells to the site of infection.

Memory T cells are long-lived T cells that provide long-term immunity against pathogens. They can quickly respond to a secondary infection by the same pathogen, leading to a faster and more robust immune response.

T cell differentiation into effector T cells involves a series of steps, including activation, proliferation, and differentiation into specific effector T cell subsets, such as cytotoxic T cells, helper T cells, and regulatory T cells.

Effector T cells include cytotoxic T cells (Tc cells), helper T cells (Th cells), regulatory T cells (Treg cells), and memory T cells. Each subset has a distinct role in the immune response.

Cytokines play a crucial role in T cell activation, proliferation, and differentiation. They are produced by various immune cells and act as signaling molecules that regulate T cell responses.