|MadSci Network: Immunology|
Monocytes are the largest white blood cells. They engulf and destroy invading bacteria and fungi and clean up debris once foreign organisms have been destroyed by other white blood cells. Monocytes can also act as antigen-presenting cells to aid in the generation of specific immune responses (both T-cell and B-cell based) to foreign antigens. Monocytes originate from very primitive cells in the bone marrow called pluripotent stem cells. These cells produce other stem cells of the myeloid stem cell line - from which the monocytes develop. The myeloid stem cells produce colonies of committed progenitor cells. Unlike stem cells, committed progenitors are only capable of developing into one specific type of mature cell. Cells passing through the final stages of maturation are called precursor cells. Monocytes develop from monoblasts through promonocytes to become mature monocytes and enter the circulatory system. Often, monocytes leave the bloodstream and enter tissues or organs, where they can differentiate into larger cells called macrophages, which have an increased capacity to destroy foreign organisms invading the body. These macrophages often exhibit very different characteristics in different kinds of tissues.
A Monocyte Maturation Chart can be found at the URL below:
Try the links in the MadSci Library for more information on Immunology.