If the first line of defense fails, the second line ‘kicks’ in. This response is also non-specific and, in turn normally carries out the same response time and time again, no matter what type of pathogen has entered the body. This includes Phagocytes, natural killer cells, inflammation, fever, macrophages, dendritic cells and mast cells all are a part of the second line of defense and compliment proteins that aid in the functions of these responses
Phagocytes are produced in the bone marrow and are the cells that carry out phagocytosis; which refers to the ingesting of organisms that are identified as non-self. The image above shows the action of a phagocyte after having detected the foreign pathogen.
Macrophage is another type of cell that carries out phagocytosis in the second line of defense. The word macrophage is derived from the greek word ‘makros’ , meaning large and ‘phagein’ which means eat. Essentially; Macrophages are big eaters.
Macrophage is another type of cell that carries out phagocytosis in the second line of defense. The word macrophage is derived from the greek word ‘makros’ , meaning large and ‘phagein’ which means eat. Essentially; Macrophages are big eaters.
Macrophages originate from leukocytes and are signaled by glycoproteins which help increase both the amount of macrophages and the rate at which the macrophages rush to the ‘site’. Once they arrive at the site the macrophages engulf the foreign pathogens; or cells that have either been infected viruses or have become cancerous, according to specific markers (antigens) of which are on the surface of the cell. As shown in the image above, after having been signaled to the area of infection by histamines; the macrophage, like phagocytes engulf the foreign pathogen through the process of endocytosis. However, macrophages, instead of releasing them through the process of exocytosis, present the foreign pathogen's antigens on its surface. T cells then get presented with the antigen, leading to a cascade of events known as the third line of defense.