Final answer:
Monocytes are large agranulocyte white blood cells known for their indented nuclei and role in the immune system, where they differentiate into macrophages or dendritic cells to respond to infections.
Step-by-step explanation:
Monocyte Characteristics and Function
A monocyte is a type of white blood cell that circulates in the blood and lymph system. Monocytes are a part of the immune system and play a key role in responding to infection. They originate from myeloid stem cells and represent 2-8 percent of the total leukocyte count. Monocytes are larger than many other white blood cells, typically measuring 12-20 µm in diameter, and are easily recognized by their indented or horseshoe-shaped nuclei after histologic staining.
When stained, these cells do not reveal granules as prominently as granulocytes do, hence monocytes fall under the agranulocyte category. Upon leaving the bloodstream and migrating into tissue, monocytes differentiate into macrophages or dendritic cells. Macrophages are known for their ability to phagocytize debris, foreign pathogens, worn-out erythrocytes, and damaged cells. They also release chemicals that attract other leukocytes to sites of infection. Macrophages may be fixed in location within tissues, or they may wander throughout the tissue fluid.
In their role within the immune response, monocytes and their derivatives perform diapedesis, which means they are capable of moving through the vessel walls to reach areas of infection or inflammation in the body's tissues.