Macrophages

What are macrophages?

Macrophages, a type of white blood cell, are key players in the immune response and help to destroy foreign invaders, including bacteria, protozoa, and tumor cells.¹ Macrophages are part of an organism’s innate immunity as well as part of specific cellular defense mechanisms.

What do macrophages do?

Macrophages are cellular scavengers. They remove dying cells and foreign invaders by a process called phagocytosis. Macrophages absorb the foreign material and then release powerful enzymes and oxidating compounds to ensure the cells being absorbed are not able to further divide and infect the organism. Macrophages are located in several organs, such as the lungs, spleen and liver, where they constantly remove debris.²

In addition to ridding the body of necrotic or disease cells, macrophages also present antigens to lymphocytes for antibody production. Once antibodies are produced, macrophages’ ability to ingest cells via phagocytosis becomes much more efficient.⁴

Macrophages play a role in the following diseases:

• Autoimmune. Macrophages are involved in pro-inflammatory immune responses. When macrophages become highly activated they can contribute towards autoimmune diseases such as rheumatoid arthritis,⁵ diabetes,⁶ and multiple sclerosis.⁷
  
  
• HIV. Macrophages play a role in HIV infection. They can continue to produce HIV viral particles after T-cell depletion. Since most antiviral treatments target T-cell, this represents a unique challenge for treating HIV positive individuals.³
  
  
• Cancer. Macrophages can stimulate cancer cells to grow during phagocytosis. Inflammatory compounds are released by macrophages and downstream pathways activate nuclear factor kappa-B (NFK-b) which enters the nucleus of the cancer cells and turns on cell cycle proteins, preventing the cell from undergoing apoptosis and thus promoting cell proliferation.²