Table 1.

Potential cell source.

Source	Definition	Drawbacks
	Donor/recipient
Autologous	Same individual	Not always available (genetic diseases, age)
Allogenic	Same species	Immunological issues
Xenogenic	Different species	Ethical issues and rejection
Syngenic or isogenic	Genetically identical individuals (clones, inbred)	Most appropriate for research with animal model
Origin/differentiation
Primary	Tissue or organ/specialized	Large expansion needed
Secondary	Cell bank	Cryopreservation/immunological issues
Embryonic stem cells (iPSCs)	Undifferentiated	Ethical issues/purification/teratoma
Adult stem cells	Commited	Selection of type/source