slides
Interleukin-3 : identification, characterization and molecular evolution
- Publication date
- 3 January 1996
- Publisher
- Blood contains large numbers of various cell types. The mature blood cell types
exert highly specialized functions such as oxygen and carbon dioxide transport,
blood clotting and defense against infections by antibody production, cell
mediated immunity and phagocytosis. Most of these mature blood cell types
have a limited life span and therefore need to be produced continuously. This
process of blood cell formation, termed hemopoiesis, is impressive since daily
approximately 1011 new blood cells are generated in man.
In steady state situations, the continuous replacement of terminally differentiated
cells is tuned with great precision but the hemopoietic system can respond
dramatically to environmental stress, such as bleeding or infection. The primary site of hemopoiesis is the bone marrow which permits the
formation of all blood cell types i.e., erythrocytes, platelets, monocytes,
neutrophils, basophils, eosinophils and lymphocytes. The continuous
replenishment of functionally mature hemopoietic cells ill vivo is strictly
dependent on the presence of a small but persistent pool of bone marrow
plmipotent hemopoietic stem cells.
The mechanism(s) controlling hemopoiesis appear to involve regulation
mediated by a group of interacting specific glycoproteins designated
hemopoietic growth factors. Furthermore, it has been implied that
microenvironmental stromal cells support hemopoiesis as well. Several mechanisms through which stromal cells affect
hemopoiesis have been postulated, i.e., a direct cell contact regulated mechanism, secretion of CSFs; expression of antagonists of differentiation-inducing
factor(s) and/or self-renewal mediators.