basophilic leukocyte

(redirected from basophilocyte)

leukocyte

 [loo´ko-sīt]
a type of blood cell that lacks hemoglobin and is therefore colorless. Leukocytes are larger in size and fewer in number than erythrocytes; normally the blood has about 8000 of them per mm3. In contrast to erythrocytes, leukocytes can move about under their own power with ameboid movement. Their chief functions are to act as scavengers and to help fight infections. Called also white cell or corpuscle and white blood cell or corpuscle. adj., adj leukocyt´ic.

Leukocytes may be classified in two main groups: the granular leukocytes are the basophils, eosinophils, and neutrophils, and the nongranular leukocytes are the lymphocytes and monocytes. About 63 per cent of all leukocytes are neutrophils; 2.5 per cent are eosinophils; and the remaining types constitute less than 1 per cent each.

Leukocytes are actively engaged in the destruction or neutralization of invading microorganisms and are quickly transported to the vicinity of infection or inflammation, so that they can move through the blood vessel wall to reach the site of injury. For this reason, their life span in the blood is usually very short. When infection is present their numbers are greatly increased and they also become more mobile and move back and forth between the blood, lymph, and tissues. The granulocytes and monocytes are phagocytic, swallowing or ingesting the foreign particles with which they come in contact. During the process of phagocytosis the phagocytes themselves are destroyed. The two types of lymphocytes involved in immunity are B lymphocytes (B cells), which play a role in humoral immunity, and T lymphocytes (T cells), which are important in cell-mediated immunity. Plasma cells are activated B cells that secrete antibodies. Monocytes are also involved in some immune processes.
Types of leukocytes.
agranular l's nongranular leukocyte.
basophilic leukocyte basophil (def. 2).
eosinophilic leukocyte eosinophil.
granular l's leukocytes containing abundant granules in the cytoplasm, including neutrophils, eosinophils, and basophils. Called also granulocyte.
neutrophilic leukocyte neutrophil (def. 2).
nongranular l's leukocytes without specific granules in the cytoplasm, including lymphocytes and monocytes. Called also agranular leukocytes.
polymorphonuclear leukocyte any fully developed, segmented granular leukocyte whose nuclei contain multiple lobes joined by filamentous connections, especially a neutrophil.

ba·so·phil·ic leu·ko·cyte

a polymorphonuclear leukocyte characterized by the presence of numerous large, coarse, metachromatic granules (dark purple or blue-black when treated with Wright or similar stains) that usually fill the cytoplasm and may almost mask the nucleus; these leukocytes are unique in that they do not usually occur in increased numbers as the result of infectious disease, and their phagocytic qualities are probably not significant; the granules, which contain numerous primary mediators, including heparin and histamine, may degranulate in response to hypersensitivity reactions and can be of significance in general inflammation; leukocytes can also synthesize and release, ab ovo, secondary mediators from arachidonic acid precursors in their membranes.
See also: mast cell.
Synonym(s): basocyte, basophilocyte

ba·so·phil·ic leu·ko·cyte

(bā'sō-fil'ik lū'kō-sīt)
A polymorphonuclear leukocyte characterized by many large, coarse, metachromatic granules (dark purple or blue-black with Wright stain) that usually fill the cytoplasm and may almost mask the nucleus; they usually do not occur in increased numbers as the result of acute infectious disease; the granules, which contain heparin and histamine, may degranulate in response to hypersensitivity reactions and can be of significance in general inflammation.
Synonym(s): mast leukocyte.

leukocyte

(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.

Function

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

Eosinophil.

agranular leukocyte

Agranulocyte.

basophilic leukocyte

Basophil.

eosinophilic leukocyte

Eosinophil.

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

Agranulocyte.

neutrophilic leukocyte

Neutrophil.

nongranular leukocyte

Agranulocyte.

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