Today’s Cell of the Day is the macrophage! Part of the innate immune system, the macrophage plays a vital role in removing invading pathogens from the host, and assisting with adaptive immune responses.
What is a macrophage?
Macrophages form part of the innate immune system; the body’s first line of defense against pathogens, alongside other leukocytes (white blood cells) such as dendritic cells. Macrophages are phagocytes, and are found in tissues all over the body. They begin life as haematopoietic stem cells (HSC), which are stem cells that produce many components of the immune system. The HSC develop into monocytes in the bone marrow, which mature into macrophages in other tissues.
What do they do?
Macrophages live up to their name: ‘macro’ meaning ‘big’, and ‘phage’ meaning ‘to eat’, and that is what they do! They are the big eaters of the immune system, and their job is to ingest the pathogens through phagocytosis, to kill them and prevent them from harming the individual. Inside the macrophage, there are many enzymes such as proteases, which digest the pathogen. Macrophages also release cytokines, to recruit other cells of the immune system, and to control levels of inflammation
Macrophages are also antigen-presenting cells (APCs). They sample antigens from pathogens at sites of infection, and deliver them to T cells and B cells (lymphocytes) that are in the peripheral lymphoid organs. This activates the lymphocytes, and will lead to the production of antibodies against the antigen, and an adaptive immune response to the pathogen.
As always, words in pink can be found in the glossary
For further reading/references: Janeways’ Immunobiology
Image from Wikimedia commons