Types of Granulocytes
- Basophils
- Eosinophils
- Neutrophils
- Mast cells
- Names derived from staining characteristics
Neutrophils
- Most abundant type of phagocyte
- Constitutes 60% to 65% of total circulating white blood cells
- Two subpopulations: neutrophil-killers and neutrophil-cagers
- One liter of human blood contains about five billion neutrophils
- Takes about thirty minutes for neutrophils to reach site of infection
Eosinophils
- Kidney-shaped lobed nuclei
- Granules contain unique toxic proteins
- Involved in killing parasites and destruction of tumor cells
- Limited ability to participate in phagocytosis
- Regulate other immune cell functions
Basophils
- Least abundant cells in bone marrow and blood
- Two lobes in nucleus, not very visible chromatin filaments
- Granules contain histamine, heparin, and other substances
- Released from bone marrow during infection
- Release histamine and prostaglandins during injury
Mast cells
- Present in tissues
- Mediate host defense against pathogens and allergic reactions
- Involved in mediating inflammation, autoimmunity, and neuroimmune system responses
Additional concepts:
- Development: Granulocytes derived from stem cells in bone marrow, differentiation process called granulopoiesis, intermediate cell types include myeloblasts and promyelocytes
- Function: Granulocytes release toxic materials on ingestion of microorganisms, examples include antimicrobial agents, enzymes, acid hydrolases, and low pH vesicles, also produce toxic nitrogen oxides and oxygen-derived products, play a crucial role in immune response against infections, deficiency of granulocytes reduces body's resistance to infections
- Granule contents: Toxic materials produced or released by degranulation, examples include antimicrobial agents, enzymes, acid hydrolases, and low pH vesicles, also toxic nitrogen oxides and oxygen-derived products, aid in the destruction of microorganisms, important for immune response against infections
- Clinical significance: Granulocytopenia is abnormally low concentration of granulocytes in blood, reduces body's resistance to infections, agranulocytosis refers to no granulocytes at all, neutropenia is deficiency of neutrophil granulocytes, granulocytes have short lifespan in circulation, making transfusion as a therapeutic strategy challenging.
Granulocytes are cells in the innate immune system characterized by the presence of specific granules in their cytoplasm. Such granules distinguish them from the various agranulocytes. All myeloblastic granulocytes are polymorphonuclear, that is, they have varying shapes (morphology) of the nucleus (segmented, irregular; often lobed into three segments); and are referred to as polymorphonuclear leukocytes (PMN, PML, or PMNL). In common terms, polymorphonuclear granulocyte refers specifically to "neutrophil granulocytes", the most abundant of the granulocytes; the other types (eosinophils, basophils, and mast cells) have varying morphology. Granulocytes are produced via granulopoiesis in the bone marrow.
| Granulocyte | |
|---|---|
 A basophilic granulocyte. | |
| Details | |
| System | Immune system |
| Identifiers | |
| MeSH | D006098 |
| FMA | 62854 |
| Anatomical terms of microanatomy | |
granule + -o- + -cyte
granulocyte (plural granulocytes)
