granulòcits

Granulòcits, or granulocytes, are a group of white blood cells characterized by cytoplasmic granules visible under light microscopy. They are part of the body's innate immune system and arise from the myeloid lineage in the bone marrow. The main subsets are neutrophils, eosinophils, and basophils.

Neutrophils are the most abundant leukocytes in peripheral blood and are professional phagocytes that rapidly migrate to sites of infection, engulf microbes, and release toxic granule contents and reactive oxygen species. They can form neutrophil extracellular traps to contain pathogens. Eosinophils participate in defense against parasitic infections and contribute to allergic reactions and asthma; their granules contain cytotoxic proteins such as major basic protein. Basophils are the least common granulocytes and release histamine and other mediators during allergic responses and parasite defenses; they share functional similarities with tissue-resident mast cells.

Granulocytes develop in the bone marrow through myelopoiesis, then enter circulation and migrate into tissues as needed. They have relatively short lifespans in the bloodstream and tissue turnover is rapid. Morphology and staining with standard hematology stains allow identification: neutrophils with multi-lobed nuclei and pale granules, eosinophils with orange-red granules, basophils with large dark granules.

Clinical relevance: quantitative abnormalities include neutrophilia or neutropenia, eosinophilia in parasitic infections or allergies, and basophilia in certain myeloproliferative disorders. In inflammation, granulocytes coordinate rapid early responses and influence later adaptive immunity.