Inflammation
Macrophages sense bacteria and other types of microorganisms in tissues these bacteria triggered to release cytokines (vasodilator) that increase the permeability of blood vessels, allowing fluid and proteins to pass into the tissues. Macrophages also produce chemokines which direct the migration of neutrophils to the site of infection this phenomenon is known as chemotaxis . The stickiness of the endothelial cells of the blood vessel wall is also changed, so that circulating cells i.e neutrophils of the immune system adhere to the wall and are able to crawl through it this phenomenon of passage of blood cells through the intact walls of the capillaries is known as diapedesis first neutrophils and then monocytes enter the tissue from a blood vessel The accumulation of fluid and cells at the site of infection causes the redness, swelling, heat, and pain known collectively as inflammation. neutrophils and macrophages are the principal inlammatory cells. Later in an immune response,activated lymphocytes can also contribute to inflammation
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