09-05-2012, 11:56 AM
hematopoietic stem cell (HSC)
Cells of immune system.ppt (Size: 2.75 MB / Downloads: 46)
Maturation
Specific gene expression to limit their pluropoitic capacity, These changes can often be tracked by monitoring the presence of proteins on the surface of the cell.
Determinism theory of haematopoiesis, which defines the nature of differentiation
The types and amounts of growth factors in the microenvironment of a particular stem cell or progenitor cell control its differentiation.
Common lymphoid progenitor cells give rise to B, T, and NK (natural killer) cells and some dendritic cells.
Myeloid stem cells generate progenitors of red blood cells (erythrocytes), many of the various white blood cells (neutrophils, eosinophils, basophils, monocytes, mast cells, dendritic cells), and platelets.
Role of transcription factor
Growth factors initiate signal transduction pathways, altering transcription factors, that, in turn activate genes that determine the differentiation of blood cells.
PU.1 commits cells to the myeloid lineage whereas
GATA-1 has an essential role in erythropoietic and megakaryocytic differentiation.
The Ikaros, Aiolos and Helios transcription factors play a major role in lymphoid development.
POLYMORPHONUCLEAR LEUKOCYTES
Their nuclei demonstrate a wide range (poly) of different shapes (morpho)
They all have distinct granules in their cytoplasm (granulocytes)
Derive from the myeloid progenitor cell, this process is regulated by cytokines, particular cytokines favoring the production of neutrophils, eosinophils, basophils or mast cells.
Neutrophils
Most common type of white blood cell, comprising about 50-70% of all white blood cells.
Provide protection from a variety of microorganisms and are arguably the most important WBC in eliminating non-viral infections by phagocytosis.
Relatively large cells (about 10–20 mm in diameter) and despite their important function, are relatively short-lived (about 2–3 days)
First type of immune cell to respond to and arrive at the site of infection, often within an hour.
Neutrophils will respond to infection inside the body, but also on the surface, as in the case of skin infections.