Granulocytes are a category of white blood cells characterized by the presence of granules in their cytoplasm. They are also called polymorphonuclear leukocytes or polymorphonuclear neutrophils (PMN, PML, or PMNL) because of the varying shapes of the nucleus, which is usually lobed into three segments. They are part of the innate immune system which comprises an immediate detense against pathogens, as contrasted to lymphocytes which take days to proliferate and become effector cells.

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