Precursor cells lineage-specific

Lineage-specific Precursor Cell Specific niches in adult tissue (Location varies for each tissue or organ) 1. Limited (Can self-renew, but only for a limited number of generations) or 2. Cannot self-renew (It no longer retains the ability to differentiate into more than one cell type), but can amplify in cell number 1. Multipotent (Can differentiate along one specific lineage [e.g., neuronal or astroglial]) or 2. Unipotent (Can only differentiate into one cell type)... 

The hematopoietic lineage originally was worked out by Injecting the various types of precursor cells into mice whose precursor cells had been wiped out by irradiation. By observing which blood cells were restored in these transplant experiments, researchers could infer which precursors or terminally differentiated cells (e.g., erythrocytes, monocytes) arise from a particular type of precursor. The first step in these experiments was separation of the different types of hematopoietic precursors. This is possible because each type produces unique combinations of cell-surface proteins that can serve as type-specific markers. If bone marrow extracts are treated with fluorochrome-labeled antibodies for these markers, cells with different surface markers can be separated in a fluorescence-activated cell sorter (see Figure 5-34). 

The proteins and cells in the blood form their own tissue system (see Chapter 44). All blood cells are derived from a common precursor, the stem cell, in the bone marrow. Different cytokine signals trigger differentiation of a particular blood cell lineage. For example, when there is a decreased supply of oxygen to the tissues, the kidney responds by releasing erythropoietin. This hormone specifically stimulates the production of red blood cells. 

---