Final answer:
Ethical concerns are lower for adult and cord blood stem cells because their collection does not involve the destruction of embryos, unlike embryonic stem cells. Also, these types of stem cells are less likely to face immunological rejection issues.
Step-by-step explanation:
There are fewer ethical issues that arise from the use of adult stem cells or cord blood stem cells in contrast to the use of embryonic stem cells. Adult stem cells are seen as ethically less controversial because they are harvested from a patient's own body, reducing concerns regarding the destruction of potential human life, which is a central ethical issue with embryonic stem cells. Similarly, cord blood stem cells, harvested from the umbilical cord at birth, are seen as a non-controversial source since collecting these cells does not harm the mother or child.
Induced pluripotent stem cells (iPSCs) are considered a promising advance in the field because they avoid ethical, legal, and immunological issues by being reprogrammed adult cells that can differentiate similar to embryonic stem cells without the need to destroy embryos. Moreover, adult stem cells and cord blood stem cells are less likely to be rejected when transplanted as they do not possess the same immunological challenges as embryonic stem cells, which may be seen as foreign by the recipient's body.