Macrophages and Your Immune System

Macrophages are a type of white blood cell that are part of your body’s defense mechanism and also part of the immune response in asthma. They are made in your bone marrow. When a foreign invader, like bacteria, enters your bloodstream, macrophages secrete certain substances in a battle to help kill the bacteria.

You can think of macrophages as one big eating machine. They identify, surround or engulf the foreign substance, and then destroy the foreign substance or cells.

In asthma, macrophages release substances that initiate and prolong hyper-responsiveness of the airways, increase mucus production and swelling, and recruit eosinophils to the lung. These substances include:

• Thromboxane
• Prostaglandins
• Platelet-activating factor

Macrophages are also thought to “clean house” in your body. These cells get rid of cells that are worn out and need to be replaced. Macrophages also play a role in wound healing and limb regeneration.

Macrophages ultimately can increase asthma symptoms such as:

• Wheezing
• Chest tightness
• Cough
• Shortness of breath

Macrophage comes from the Greek words Macro meaning “large” and Phage meaning “to eat.” When a macrophage encounters something foreign, it tends to surround it and destroy it. These cells start off as what is termed a monocyte in the bloodstream and will develop into an appropriate macrophage when the body senses something awry.

Your body is really smart. The monocytes circulate in your bloodstream normally. When your body detects an infection, the monocytes travel to that part of the body and begin their transformation into a macrophage. The monocyte can transform into several different kinds of macrophages depending on what the body needs.

The macrophages will survive for several months after they are created. Additionally, the body will remember the infection so it can react more quickly should the infection occur again.

The process of the macrophage surrounding, engulfing and killing foreign substances is called phagocytosis. It comes from the Greek words “phagein” meaning to eat, “kytos” or cell and “osis” which means process.

Importantly, the macrophages are able to identify self from non-self so that they do not harm or damage cells of normal form or function.

Other Cells and Asthma

Macrophages are just one of the many cell types that play a role in your asthma. Others include:

• Basophils
• Eosinophils
• Lymphocytes
• Mast Cells
• Neutrophils
• Monoclonal Antibodies
• IgE