Degranulation is a cellular process that releases antimicrobial cytotoxic or other molecules from

secretory 440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classica ...

vesicles called granules found inside some cells. It is used by several different cells involved in the

immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splinte ...

, including granulocytes (

neutrophil Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying ...

s, basophils, and eosinophils) and mast cells. It is also used by certain

lymphocyte A lymphocyte is a type of white blood cell (leukocyte) in the immune system of most vertebrates. Lymphocytes include natural killer cells (which function in cell-mediated, cytotoxic innate immunity), T cells (for cell-mediated, cytotoxic a ...

s such as natural killer (NK) cells and

cytotoxic T cell A cytotoxic T cell (also known as TC, cytotoxic T lymphocyte, CTL, T-killer cell, cytolytic T cell, CD8+ T-cell or killer T cell) is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected by intracellular p ...

s, whose main purpose is to destroy invading microorganisms.

Mast cells

Antigens interact with IgE molecules already bound to high affinity Fc receptors on the surface of mast cells to induce degranulation, via the activation of tyrosine kinases within the cell. The mast cell releases a mixture of compounds, including

histamine Histamine is an organic nitrogenous compound involved in local immune responses, as well as regulating physiological functions in the gut and acting as a neurotransmitter for the brain, spinal cord, and uterus. Since histamine was discover ...

, proteoglycans,

serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and va ...

, and serine proteases from its cytoplasmic granules.

Eosinophils

In a similar mechanism, activated eosinophils release preformed mediators such as major basic protein, and

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

s such as peroxidase, following interaction between their Fc receptors and IgE molecules that are bound to large

parasite Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson h ...

s like helminths.

Neutrophils

Four kinds of granules exist in neutrophils that display differences in content and regulation. Secretory vesicles are the most likely to release their contents by degranulation, followed by gelatinase granules,

specific granule Specific granules are secretory vesicles found exclusively in cells of the immune system called granulocytes. It is sometimes described as applying specifically to neutrophils, and sometimes the term is applied to other types of cells. These gra ...

s, and azurophil granules.

Cytotoxic T cells and NK cells

Cytotoxic T cells and NK cells release molecules like perforin and granzymes by a process of directed exocytosis to kill infected target cells.

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