CD4+

CD4+

CD4+ T cells, also known as CD4-positive T cells, are a type of white blood cell that play a significant role in the immune system. They are a subset of T lymphocytes that express the CD4 glycoprotein on their surface. These cells are crucial for the adaptive immune response, as they help orchestrate the body's defense against pathogens.

Function

CD4+ T cells are often referred to as "helper" T cells because they assist other cells in the immune system. They do this by:

• Activating B cells: CD4+ T cells help B cells to produce antibodies, which are proteins that can neutralize pathogens.
• Activating cytotoxic T cells: They aid in the activation of CD8+ T cells, which can directly kill infected cells.
• Releasing cytokines: These cells secrete cytokines, which are signaling molecules that mediate and regulate immunity, inflammation, and hematopoiesis.

Subtypes

CD4+ T cells can differentiate into various subtypes, each with a unique role in the immune response:

• Th1 cells: These cells are involved in the response against intracellular bacteria and viruses. They produce cytokines like IFN-γ.
• Th2 cells: They are important for the defense against extracellular parasites and are involved in allergic responses. They produce cytokines such as IL-4, IL-5, and IL-13.
• Th17 cells: These cells are involved in the defense against fungi and bacteria and are associated with autoimmune diseases. They produce IL-17.
• Regulatory T cells (Tregs): These cells help maintain immune tolerance and prevent autoimmune disease by suppressing immune responses.

Clinical Significance

CD4+ T cells are a key marker in the diagnosis and monitoring of HIV/AIDS. The virus targets and destroys these cells, leading to a weakened immune system. The CD4 count is used to assess the stage of HIV infection and guide treatment decisions.

Also see

• T lymphocyte
• Immune system
• HIV/AIDS
• Cytokine
• B cell