nongranular leukocyte

(redirected from agranular leukocyte)
Also found in: Dictionary, Thesaurus, Encyclopedia.
Related to agranular leukocyte: neutrophil

non·gran·u·lar leu·ko·cyte

a general, nonspecific term frequently used with reference to lymphocytes, monocytes, and plasma cells; although the cytoplasm of a lymphocyte or monocyte contains tiny granules, it is "nongranular" in comparison with that of a neutrophil, basophil, or eosinophil.
See also: leukocyte.
Synonym(s): agranular leukocyte
Farlex Partner Medical Dictionary © Farlex 2012

non·gran·u·lar leu·ko·cyte

(non-granyū-lăr lūkō-sīt)
General, nonspecific term frequently used with reference to lymphocytes, monocytes, and plasma cells.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


(loo'ko-sit?) [ leuko- + -cyte]
Any of several kinds of colorless or nearly colorless cells of the immune system that circulate in the blood and lymph. Leukocytes comprise granulocytes and agranulocytes. Synonym: white blood cell; white cell; white blood corpuscle; white corpuscle See: blood for illus

Neutrophils, 55% to 70% of all leukocytes, are the most numerous phagocytic cells and are a primary effector cell in inflammation. Eosinophils, 1% to 3% of total leukocytes, destroy parasites and are involved in allergic reactions. Basophils, less than 1% of all leukocytes, contain granules of histamine and heparin and are part of the inflammatory response to injury. Monocytes, 3% to 8% of all leukocytes, become macrophages and phagocytize pathogens and damaged cells, esp. in the tissue fluid. Lymphocytes, 20% to 35% of all leukocytes, have several functions: recognizing foreign antigens, producing antibodies, suppressing the immune response to prevent excess tissue damage, and becoming memory cells.

Leukocytes are formed from the undifferentiated stem cells that give rise to all blood cells. Those in the red bone marrow may become any of the five kinds of leukocytes. Those in the spleen and lymph nodes may become lymphocytes or monocytes. Those in the thymus become lymphocytes called T lymphocytes.


Leukocytes are the primary effector cells against infection and tissue damage. They not only neutralize or destroy organisms, but also act as scavengers, engulfing damaged cells by phagocytosis. Leukocytes travel by ameboid movement and are able to penetrate tissue and then return to the bloodstream. Their movement is directed by chemicals released by injured cells, a process called chemotaxis. After coming in contact with and recognizing an antigen, neutrophils or macrophages phagocytize (engulf) it in a small vacuole that merges with a lysosome, to permit the lysosomal enzymes to digest the phagocytized material. When leukocytes are killed along with the pathogenic organisms they have destroyed, the resulting material is called pus, commonly found at the site of localized infections. Pus that collects because of inadequate blood or lymph drainage is called an abscess.

Microscopic examination: Leukocytes can be measured in any bodily secretion. They are normally present in blood and, in small amounts, in spinal fluid and mucus. The presence of leukocytes in urine, sputum, or fluid drawn from the abdomen is an indication of infection or trauma. The type of WBC present is identified by the shape of the cell or by the use of stains (Wright's) to color the granules: granules in eosinophils stain red, those in basophils stain blue, and those in neutrophils stain purple.

Clinically, WBC counts are important in detecting infection or immune system dysfunction. The normal WBC level is 5000 to 10,000/mm3. An elevated (greater than 10,000) leukocyte count (leukocytosis) indicates an acute infection or inflammatory disease process (such as certain types of leukemia), whereas a decrease in the number of leukocytes (less than 5000) indicates either immunodeficiency or an overwhelming infection that has depleted WBC stores. In addition to the total WBC count, the differential count is also frequently important. A differential count measures the percent of each type of WBC (e.g., neutrophils, monocytes, lymphocytes). The differential also measures the number of immature cells of each cell type as an indication of production by the bone marrow. Immature cells are called “blasts” (e.g., lymphoblasts, myeloblasts). During infections or in certain types of leukemia, blasts may be present in peripheral blood. See: inflammation

acidophilic leukocyte


agranular leukocyte


basophilic leukocyte


eosinophilic leukocyte


granular leukocyte

A leukocyte containing granules in cytoplasm.

heterophilic leukocyte

A neutrophilic leukocyte of certain animals whose granules stain with an acid stain.

lymphoid leukocyte


neutrophilic leukocyte


nongranular leukocyte


polymorphonuclear leukocyte

Abbreviation: PMN
A white blood cell with a nucleus made of two or more lobes, i.e., the granular leukocytes: neutrophils, eosinophils, or basophils.
Synonym: polysegmented neutrophil. See: basophil; eosinophil; neutrophil
Medical Dictionary, © 2009 Farlex and Partners