Co-stimulation

Co-stimulation is a process that involves the activation of T cells in the immune system. This process is crucial for the immune response, as it helps to ensure that the immune system is able to effectively fight off pathogens and other harmful substances. Co-stimulation is typically achieved through the interaction of two or more proteins on the surface of the T cell and another cell, such as an antigen-presenting cell (APC).

Mechanism of Co-stimulation

The process of co-stimulation begins when an APC presents an antigen to a T cell. This is achieved through the interaction of the Major Histocompatibility Complex (MHC) on the APC and the T cell receptor (TCR) on the T cell. However, this interaction alone is not sufficient to fully activate the T cell.

In addition to the MHC-TCR interaction, a second interaction must occur between the CD28 protein on the T cell and the B7 protein on the APC. This second interaction, or co-stimulation, provides the necessary signal for the T cell to become fully activated.

Once activated, the T cell can then proliferate and differentiate into effector T cells, which can carry out various functions in the immune response, such as killing infected cells or helping other immune cells to respond to the antigen.

Importance of Co-stimulation

Co-stimulation is crucial for the proper functioning of the immune system. Without co-stimulation, T cells may become anergic, or unresponsive, which can lead to a weakened immune response.

Furthermore, co-stimulation plays a key role in the immune system's ability to distinguish between self and non-self antigens. This is because co-stimulation is typically only provided by APCs that have encountered a non-self antigen. This helps to prevent the immune system from mistakenly attacking the body's own cells.

See Also

• T cell
• Antigen-presenting cell
• Major Histocompatibility Complex
• CD28
• B7

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