CD4+ T cells

CD4+ T Cells

CD4+ T cells, also known as T helper cells, are a type of lymphocyte that play a crucial role in the immune system. They are a subset of T cells that express the CD4 glycoprotein on their surface. These cells are essential for orchestrating the immune response by activating and directing other immune cells.

Structure and Function

CD4+ T cells are characterized by the presence of the CD4 receptor, which is a co-receptor that assists the T cell receptor (TCR) in recognizing antigens presented by major histocompatibility complex (MHC) class II molecules. This interaction is critical for the activation of CD4+ T cells.

Once activated, CD4+ T cells differentiate into various subsets, each with distinct functions:

• 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: They assist in the activation of B cells and are crucial for the humoral immune response, particularly in the defense against extracellular parasites.
• T helper 17 (Th17) cells: These cells are involved in the defense against fungi and bacteria and play a role in inflammatory responses.
• Regulatory T (Treg) cells: These cells help maintain immune tolerance and prevent autoimmune diseases by suppressing excessive immune responses.

Role in Disease

CD4+ T cells are central to the immune response, and their dysfunction can lead to various diseases:

• HIV/AIDS: The human immunodeficiency virus (HIV) targets CD4+ T cells, leading to their depletion and resulting in acquired immunodeficiency syndrome (AIDS). The loss of CD4+ T cells impairs the immune system, making individuals susceptible to opportunistic infections.
• Autoimmune diseases: Dysregulation of CD4+ T cell function can contribute to autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, and type 1 diabetes.
• Allergies and asthma: Th2 cells are involved in allergic responses, and their overactivation can lead to conditions such as asthma.

Clinical Significance

The measurement of CD4+ T cell counts is a critical component in the management of HIV/AIDS. It helps in assessing the immune status of patients and guiding treatment decisions. Antiretroviral therapy (ART) aims to restore and maintain CD4+ T cell counts to prevent opportunistic infections.

Research and Therapeutic Applications

Research on CD4+ T cells continues to provide insights into their role in health and disease. Therapeutic strategies targeting CD4+ T cells include:

• Immunotherapy: Modulating CD4+ T cell responses is a strategy in cancer immunotherapy, where enhancing the activity of these cells can help in the elimination of tumor cells.
• Vaccines: CD4+ T cells are crucial for the development of effective vaccines, as they help in the generation of robust and long-lasting immune responses.

See Also

• CD8+ T cell
• Immune system
• Antigen presentation

External Links

• CD4+ T Cells in the Immune System
• HIV/AIDS Fact Sheet