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Degranulation is a term used generally to refer to the loss or breakup of granules. In cell biology, it describes a very specific process which takes place on the cellular level, in which granules contained inside specialized cells break up to release their contents, akin to bath beads bursting open in the tub. Degranulation can sometimes be observed under very high powered microscopes, and researchers have learned a great deal about the mechanism of the process and how it works in different types of cells.
Two cell types which include granules are mast cells and granulocytes. Other types of cells can hold granules, sometimes called secretory vesicles, as well. These cells are involved in immune responses. The immune system is designed to identify foreign bodies so that they can be targeted for destruction, whether they come in the form of bacteria in the body, viruses which hijack cells and use them for replication, or anything in between.
In the degranulation process, a cell which contains granules is activated through a series of reactions, which can vary in nature depending on which type of cell is involved. When activated, the cell's granules burst open, releasing compounds which have cytotoxic, or cell-killing, effects. These compounds can be used to eliminate bacteria and other foreign cells in the body, and also to kill infected cells which pose a risk to the body because they are carriers of infectious agents.
The immune system is remarkably good at what it does. It can respond very quickly to potential threats and it learns to recognize new threats all the time so that it can keep the body protected from bacteria, viruses, fungi, and other microorganisms. Degranulation is only one of the defenses available to the immune system which can be launched when a threat is detected. The body constantly produces new cells capable of degranulation so that they will be available when they are needed for immune system activities.
Some infectious agents are capable of thwarting the immune system and the various responses it has developed to threats. These agents may hijack the immune system itself, act to depress the immune system so that it cannot respond, or work so quickly that the body does not have time to mount an adequate defense.
Interestingly, the degranulation used by the body is actually mimicked by some pharmaceutical products. These products are filled with tiny capsules which are designed to release when they reach a set point in the body. Such drugs are often used to deliver oral medications which would be damaged in the stomach; the other layers of the drug keep the granules inside safe so that they will open up in the intestinal tract.