One of the most important cells of our immune system are the leukocytes or white blood cells (WBCs). These cells are free from hemoglobin and belong to the reticuloendothelial cell system. White blood cells are divided into two types, granular and agranular leukocytes. The agranular ones contain a single nucleus while granular ones are polynucleated cells. In the following paragraphs, we shall concentrate solely on granular leukocytes and their types.
What are Granular Leukocytes
These cells have multilobed nuclei that function against non-specific invading agents in the body. They make up about 50 to 70% of all white blood cells. When stained, one can view differently stained granules in the cytoplasm under light microscopy. These granules are actually membrane bound enzymes. These enzymes tend to engulf the endocytosed particles and help in their digestion.
There are three types of these leukocytes. These include - neutrophils, basophils and eosinophils. These types are named according to their staining properties. We shall have a look at their functions as we cover each type of white blood cell in detail in the paragraphs below.
Also called neutrophils or polymorphonuclear neutrophils (PMNs), they are the most widely found white blood cells in mammals. They are divided into two types, segmented neutrophils and banded neutrophils. These cells are found in blood and function as phagocytes. Their lifespan is about 6 hours only. When a bacterial infection or certain cancers and other environmental factors lead to inflammation, these are the first cells to respond. They migrate towards the site of inflammation through a process called chemotaxis. Their presence indicates acute inflammation. The yellow or whitish appearance of pus is also due to the predominant presence of the neutrophils. The function of neutrophil granuloytes is to migrate to the site of infection. They begin to recruit and activate other WBCs and attack the invading micro-organism. These cells tend to attack micro-organisms by phagocytosis, release of antimicrobials and creation of neutrophil extracellular traps.
Eosinophils or eosinophiles are 'acid-loving' leukocyte cells. They tend to show strong affinity towards eosin, a red dye that makes them appear red. Eosinophils make up 1 to 6% of the WBCs. They are present in the medulla and at the junction between the medulla of the thymus and cortex. These cells are also found in the gastrointestinal tract, ovary, uterus, spleen and lymph nodes. The function of the eosinophils is to fight off multicellular parasites and certain infections. They also help in controlling allergies and asthma along with mast cells. When in circulation, they survive for just 8 to 12 hours.
Basophils form only 0.01% to 0.3% of the WBCs circulating in blood. These cells are basophilic in nature, i.e., they can be stained using the basic dyes. Their function is to appear during inflammatory reactions that lead to allergy signs. They contain heparin that prevents blood clotting. They have a role in parasitic infections as well as allergies. These cells release histamine that leads to inflammatory responses. Eosinophils tend to release a toxic basic protein that helps in killing parasites. They also function as antigen presenting cells, regulate immune cell functions and help in repair of damaged tissues as well as destroy tumor cells.
The basic function of these cells is to respond to an infection or allergen in the body. These cells have a very short lifespan. Hope the above information was useful in learning about white blood cells with granulated cells.