CD4+ T cell

CD4+ T Cell

CD4+ T cells, also known as CD4-positive T cells, are a type of T lymphocyte that play a crucial role in the immune system. They are a subset of white blood cells that are essential for orchestrating the immune response by activating and directing other immune cells. CD4+ T cells are characterized by the presence of the CD4 glycoprotein on their surface, which serves as a co-receptor that enhances their ability to recognize antigens presented by antigen-presenting cells (APCs).

Function

CD4+ T cells are primarily involved in the adaptive immune response. They are often referred to as "helper T cells" because they assist other cells in the immune system. Upon activation by an APC, CD4+ T cells can differentiate into various subsets, including:

• Th1 cells: These cells are involved in the activation of macrophages and are important for the defense against intracellular pathogens such as viruses and certain bacteria.
• Th2 cells: These cells help activate B cells to produce antibodies and are important in the defense against extracellular pathogens, such as parasites.
• Th17 cells: These cells are involved in the defense against fungi and bacteria and play a role in inflammatory responses.
• T regulatory cells (Tregs): These cells help maintain immune tolerance and prevent autoimmune diseases by suppressing excessive immune responses.

Activation

CD4+ T cells are activated through the interaction with major histocompatibility complex (MHC) class II molecules on APCs. The T cell receptor (TCR) on CD4+ T cells recognizes specific antigens presented by MHC class II molecules. This interaction, along with co-stimulatory signals, leads to the activation and proliferation of CD4+ T cells.

Clinical Significance

CD4+ T cells are a critical component of the immune system, and their dysfunction can lead to various diseases. For example, in HIV/AIDS, the virus specifically targets and depletes CD4+ T cells, leading to immunodeficiency. Monitoring CD4+ T cell counts is crucial in managing HIV-infected patients.

CD4+ T cells are also involved in autoimmune diseases, where they may mistakenly attack the body's own tissues. Understanding the regulation and function of CD4+ T cells is important for developing therapies for autoimmune conditions and for enhancing immune responses against infections and cancers.

Also see

• T lymphocyte
• Immune system
• Antigen-presenting cell
• HIV/AIDS
• Autoimmune disease