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Inflammation and the immune system

What is inflammation?

Inflammation is the body's normal response to injuries or infections. You may often hear the words infection and inflammation together, but they mean very different things. Infection refers to the invasion and multiplication of a pathogen within the body, while inflammation is the body's protective response against infection. Inflammation is a complex process involving various types of immune cells, clotting proteins and signaling molecules, all of which change over time.

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Inflammation is the normal response of your body’s immune system to injuries and harmful things that enter your body. Immune cells quickly react to the damaged area to fix the problem. During the process, you may feel symptoms like pain, warmth, swelling and redness.

The cells of our immune system immediately travel to the site of injury or irritation and cause inflammation. This includes a widening of local blood vessels that result in an outflow of fluid and immune cells into surrounding tissues. This process often causes temporary discomfort, resulting in what physicians refer to as the four cardinal signs of inflammation:

  • Warmth
  • Redness
  • Swelling
  • Pain

Normally, inflammation disappears on its own after the irritation has been removed and the body is adequately protected. In some conditions, however, inflammation is the disease; it starts in the absence of harmful irritations and continues with no resolution. This leads to organ function problems. Examples of long-term inflammatory conditions include:

Tools of our immune system

Types of White Blood Cells
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All white blood cells are produced in the bone marrow. These cells help to fight infection in your body.
  1. White blood cells, also known as leukocytes, are the cells of the immune system. White blood cells help fight infection by attacking invaders and consuming infected or dead cells. The body has various types of white blood cells, but all are produced in the bone marrow (the soft middle part of our bones).

  2. Lymphocytes are a special type of white blood cell. There are two major classes of lymphocytes: T cells and B cells. B cells make up about 5-15% of the lymphocytes in our bodies. B cells develop in the bone marrow and are responsible for producing antibodies. There are thousands of different B cells in our body, each of which produces a unique antibody. T cells develop in the thymus and help coordinate a rapid and tailored immune response to specific infectious organisms.

  3. Antibodies are proteins that are secreted from B cells. Antibodies help the immune system recognize foreign proteins that do not belong to the body. In doing so, they initiate an inflammatory response and clear the body of the invader.

  4. Neutrophils are the white blood cells that arrive first at the site of injury. They release chemical signals that attract other immune cells in an effort to help protect the body.

  5. Monocytes are special white blood cells that mature into cells called macrophages. Macrophages respond to signals released from neutrophils, and they are capable of eating and destroying potential pathogenic invaders in a process called phagocytosis.

  6. Eosinophils & Basophils are less ubiquitous white blood cells that have roles in parasite infections.

Susanne Benseler, MD

Manisha Sickand, MSc, MD Candidate 2015

Marinka Twilt, MD