CD4 cell

An important type of immune cell involved in the body's response to infection

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CD4 cells, also known as T-helper cells, are a type of white blood cell that play a significant role in the immune system. They are a subset of lymphocytes and are crucial in the body's defense against infections. CD4 cells are primarily responsible for signaling other cells in the immune system to perform their functions, such as attacking infected cells or producing antibodies.

Structure and Function

CD4 cells are characterized by the presence of the CD4 glycoprotein on their surface. This protein acts as 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 cells differentiate into various subsets, including Th1, Th2, Th17, and T regulatory cells, each with distinct roles in orchestrating the immune response.

Activation

The activation of CD4 cells occurs when they encounter an antigen presented by an APC. This interaction, along with co-stimulatory signals, leads to the proliferation and differentiation of CD4 cells into effector cells. These effector cells then secrete cytokines that help activate other immune cells, such as B cells and cytotoxic T cells.

Role in Disease

CD4 cells are critical in the immune response to infections, particularly viral infections. However, they are also the primary target of the Human Immunodeficiency Virus (HIV), which leads to their depletion and the subsequent weakening of the immune system, resulting in Acquired Immunodeficiency Syndrome (AIDS).

Clinical Significance

The number of CD4 cells in the blood is an important marker of immune function. In individuals with HIV, CD4 cell counts are used to monitor disease progression and guide treatment decisions. A normal CD4 count ranges from 500 to 1,500 cells per cubic millimeter of blood. A count below 200 cells/mm³ is indicative of AIDS.

Research and Therapeutics

Research into CD4 cells has led to the development of various immunotherapies and vaccines. Understanding the mechanisms of CD4 cell activation and differentiation is crucial for designing strategies to enhance immune responses against infections and cancer.

Also see

• CD8 cell
• Immune system
• HIV/AIDS
• Lymphocyte
• T cell receptor