Pluripotent hematopoietic stem cells multiply and differentiate within the hematopoietic system, which is a hierarchy of cells. HSCs eventually give rise to adult blood cells after a number of stages.
1. Hematopoietic stem cells
2. Progenitor cells
a. Multipotent progenitor cells
b. Committed (unipotent) progenitor cells
3. Precursor cells
4. Maturing and mature cells
Hematopoietic Stem Cells (HSC)
Hematopoietic Stem Cells (HSC) are undifferentiated, mononuclear cells that possess the ability to differentiate into all blood cell lineages.
HSCs have two essential characteristics:
• Self-renewal: HSCs can divide into several cells to produce more stem cells.
• Differentiation: HSCs have the ability to differentiate into common myeloid and common lymphoid progenitors, two types of lineage-specific multipotent progenitor cells.
Note: The stem cells have the potential to differentiate into a variety of tissue types in addition to blood cells (e.g. neural, muscle, liver, and vascular cells). Transdifferentiation is the term for this shift in a cell's differentiation from one type to another, and developmental plasticity is the ability of a cell to transdifferentiate into many lineages.
Progenitor Cells
The HSCs move into the progenitor cell compartment, which is the next compartment, after committing to develop. There are primarily two kinds of cells in this compartment.
• Lineage-specific multipotent progenitor cells
• Dedicated (unipotent) stem cells
When cultivated in culture, both multipotent and unipotent bone marrow cells have the capacity to produce clones, or groupings made up of particular types of mature cells. These cells are called colony forming units (CFU).
Multipotent stem cells: Early progenitors with myeloid potential and early progenitors with lymphoid potential are the two categories into which these fall.
• Two primary types of multipotent progenitor cells with restricted differentiation are produced by further dividing early progenitor cells with myeloid potential. They are as follows:
Three types of committed (unipotent) progenitor cells are produced by CFU b/Mg/E (multipotent) cells.
◆ Colony-forming unit-erythrocyte cells, abbreviated CFU-E. Erythropoietin's action is most susceptible to it.
◆ CFU-Mg (colony-forming unit-megakaryocyte) cells
The CFU-Mix cells, also known as CFU-Baso (colony-forming unit-basophil) cells, differentiate into three distinct types of committed (unipotent) progenitor cells.
◆ Colony-forming unit-granulocyte cells, which are the antecedents of neutrophils
◆ Monocyte precursors, also known as CFU-M (colony-forming unit-macrophage) cells, and
macrophages.
The cells that precede eosinophils are called CFU-Eo (colony-forming unit-eosinophil) cells.
• Three progenitor cells are produced from an early progenitor with lymphoid potential cell.
- Pro-T cells that undergo T cell differentiation.
Pro-NK cells that undergo NK cell differentiation.
- Pro-B cells that undergo B cell differentiation.
Antecedent Cells
Precursor cells are defined as immature hematopoietic cells that have acquired distinguishable morphological, cytochemical, or immunological characteristics of a single lineage. The development of unipotent progenitor cells into precursor cells is the next stage of hematopoiesis. Each lineage's first physically identifiable precursor cell is named by appending the suffix "blast" to the lineage type (for example, lymphoblast to lymphoid lineage).
Fully Grown Cells
Mature blood cells are ultimately produced by the precursor cells and are sent into the bloodstream from the bone marrow.
