There are various lines of defenses that the body establishes to keep disease causing microorganisms at bay. All of this is mediated on a cellular level by one of the blood components known as white blood cells, or leukocytes. Everyone knows that the main function of white blood cells is to protect the body from outside agents that tend to cause diseases. There are different types of leukocytes, and each one is adept at carrying out a specific function against a specific type of pathogen.
Structure and Function
As mentioned earlier, there are specific types of cells that are responsible for combating a specific type of pathogen. In general, it can be said that there are two broad types of white blood cells - granulocytes and agranulocytes. Granulocytes include neutrophils, eosinophils and basophils. These cells usually have multi-lobed nuclei, along with granules in their cytoplasm. Agranulocytes, that is, cells that do not have any granules in their cytoplasm include cells like monocytes, lymphocytes and macrophages. Given below are details regarding the functions of each of these cell types.
|Neutrophils||These are one of the first cells to aggregate at a site of infection, due to which they have often been branded as the first line of defense in the body. They attack bacteria and fungi that enter the body and are often killed in the process of fighting these pathogens. These are involved in acute inflammatory responses and act by phagocytosing the pathogen. A decrease in the number of neutrophils is known as neutropenia.|
|Eosinophils||These are granulocytes that are primarily involved with parasitic infections. Any sudden increase in the count of eosinophil usually indicates the presence of a parasite in the body. They are also present in abundance when a person has an allergic response to something. Thus, when there is an elevated white blood cell count of eosinophils, then it may also indicate asthma or hay fever.|
|Basophils||These are blood cells which are primarily released in large numbers when a person has an allergic response. It releases histamine, one of the main chemicals released in such a response. It is also involved in the antigen responses in the body.|
|Lymphocytes||These are primarily involved in making antibodies which bind with a pathogen so as to destroy them. They also mediate immune responses and kill tumor and cancerous cells.|
|Monocytes||These act on pathogens, and aid the neutrophils in carrying out their functions.|
|Other Leukocytes||Other types of leukocytes include macrophages, whose main task is to engulf pathogens by phagocytosis and dendritic cells, which basically aid in activating the lymphocytes when there is need for an antigen reaction.|
Most of the granulocytes are responsible for attacking pathogens head on. There are certain qualities with the help of which these cells function. These include chemotaxis, wherein a cell manages to get to know where the pathogens are with the help of chemicals which guide them to the location of the pathogen. Also, the phagocytosis process, where the white blood cell engulfs dangerous pathogens, also helps to protect the surrounding cells and structures from the harmful effects of pathogens. Any kind of changes in the count of WBCs, like a sudden decrease in the count, as is seen in leukopenia and agranulocytosis, compromises the immune system of the person and places him in grave danger of suffering from a disease. On the other hand, an increased white blood cell count is indicative of a disease or infection in the body, which these cells are trying to curb.