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Antigen-presenting cells

Related Terms

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Background

  • Antigen-presenting cells (APC) are specialized white blood cells that help fight off foreign substances that enter the body. These cells send out signals to T-cells (other immune system cells) when an antigen enters the body. Each type of T-cell is specially equipped to deal with different pathogens, which may be a bacteria, virus or toxin.
  • First, the APC engulfs the antigen. Enzymes inside the APC break down the antigen into smaller particles. The processed antigens are transported to the surface of the APC, bound with either an MHC (major histocompatibility complex) class I or class II molecule. This complex forms epitopes (part of a foreign substance that can be recognized by the immune system), which the T-cell receptor (TCR) recognizes and binds to.
  • The APCs are divided into two categories - professional and non-professional APCs. Professional APCs express MHC class II while non-professional APCs express MHC class I. Only professional APCs are able to activate a helper T-cell that has never encountered its antigen before. There are three main types of professional antigen-presenting cells - macrophages, dendritic cells and B-cells. These cells are able to engulf the antigen quickly during a process called phagocytosis. Once the T-cell recognizes and binds to the MHC molecule complex, the APC sends out an additional co-stimulatory signal to activate the T-cell.
  • Non-professional APCs include fibroblasts (skin cells), thymic epithelial cells, thyroid epithelial cells, glial cells (brain cells), pancreatic beta cells and vascular endothelial cells.
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Macrophages

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Dendritic Cells

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B-Cells

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Interaction With T-Cells

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.