Replacing Cells - Biotechnology and Your Health: Pharmaceutical Applications - page 118

Stop and Consider
Why do some scientists view adult stem cells as more promising
than embryonic stem cells?
Immune System Problems
The use of specialized cells produced from embryonic stem cells
faces another challenge: The patient's immune system may destroy
them. Because of inherited transplant proteins, specialized cells
developed from embryonic stem cells may be attacked and destroyed
by the immune system of the person who receives such cells. Some
scientists believe that this kind of an attack would not happen,
because they have found that embryonic stem cells and the special-
ized cells produced from them in the laboratory do not make enough
of the transplant proteins to trigger such an attack. If this is not
the case, however, there may be a possible solution: a process called
therapeutic cloning . In therapeutic cloning, the nucleus of a donated
egg cell is replaced with a nucleus from a patient's cell. The resulting
cell would be grown in the lab through several rounds of cell
division to produce a very early embryo from which embryonic stem
cells would be taken and treated further to generate the specialized
cells for treatment, whether insulin-producing cells, heart muscle
cells to replace cells damaged in a heart attack, or something else.
Because the nucleus used for the technique is taken from a somatic
cell , a cell not destined to produce eggs or sperm, the process is also
called somatic nuclear transfer ( SNT ). The embryo created in the lab
would be, in genetic characteristics, a clone of the donor of the
nucleus, the patient him- or herself. The transplant proteins made by
the specialized cells would perfectly match the patient's because the
genes directing their production would be the patient's own.
Ethical Arguments
Research on human embryonic stem cells and therapeutic cloning