Table 2.

Comparison of cellular reagents for use in human experimental biology and clinical medicine

Cell source	Advantages	Disadvantages	Application
Differentiated primary cells	Verifiable phenotype Physiologically relevant Well characterized No/very low tumor risk	Limited supply Can be difficult to harvest Limited culture time Graft-versus-host reactions (nonautologous)	Transplantation and grafting Mechanistic studies in vitro
Adult multipotent progenitors	Relatively easy to harvest Available in large quantities No ethical issues	Relatively poorly defined mechanisms of action Limited markers for analysis Limited culture time Limited plasticity	Cell therapy strategies Mechanistic studies in vitro Tissue engineering
Pluripotent stem cells	Plasticity to all three germ layers Permits organogenesis strategies Indefinite culture time Good model for developmental biology No ethical issues for iPS technology	Ethical issue associated with ES cells Time-consuming approval processes Risk of tumorigenesis High cost to culture Labor intensive to culture Immature/embryonic phenotype	Cell therapy strategies Tissue engineering Organogenesis Disease modeling in vitro Developmental biology
Immortal cells	Available in large quantities Indefinite culture time Commercially available Cost effective	High risk of tumorigenesis Not useful in the clinical setting	Virus production In vitro cancer research

The selection of cells for use in basic science or translational technologies is often an important decision. Considerations to be contemplated are whether the cells to be used in experimentation are relevant to the physiological equivalent, whether they are plentiful enough for the intended application, and whether they present special concerns like ethical issues.