CD4+ cells

CD4+ T cells, also known as T helper cells, are a type of white blood cell that play a crucial role in the immune system. They are a subset of T cells that express the CD4 glycoprotein on their surface. CD4+ T cells are essential for the adaptive immune response, as they help activate and direct other immune cells, including B cells, CD8+ T cells, and macrophages.

Structure and Function

CD4+ T cells are characterized by the presence of the CD4 receptor on their surface. This receptor is a co-receptor that assists the T cell receptor (TCR) in recognizing antigens presented by antigen-presenting cells (APCs) in the context of major histocompatibility complex (MHC) class II molecules. Upon activation, CD4+ T cells differentiate into various subsets, including:

• T helper 1 (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.
• T helper 2 (Th2) cells: These cells help activate B cells to produce antibodies and are important in the defense against extracellular pathogens, such as helminths.
• T helper 17 (Th17) cells: These cells are involved in the defense against extracellular bacteria and fungi and play a role in autoimmune diseases.
• Regulatory T cells (Tregs): These cells help maintain immune tolerance and prevent autoimmunity.

Role in Disease

CD4+ T cells are critical in the immune response, but they can also be involved in autoimmune diseases when they mistakenly target the body's own tissues. Additionally, CD4+ T cells are the primary target of the human immunodeficiency virus (HIV), which leads to their depletion and the progression to acquired immunodeficiency syndrome (AIDS).

Clinical Significance

The number of CD4+ T cells in the blood is an important marker of immune function, particularly in individuals with HIV/AIDS. A normal CD4+ T cell count ranges from 500 to 1,500 cells per cubic millimeter of blood. A count below 200 cells/mm³ is one of the criteria for the diagnosis of AIDS.

Also see

• T cell
• B cell
• Immune system
• HIV
• Autoimmune disease

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