Immunology of Stem Cells
Stem cells are unique in that
1) they self-renew, and
2) they are capable of differentiating into cells of different tissues and organs.
Stem cells with these unique properties are found in embryos and in various tissues of fetuses and adults. While it is unknown whether embryonic stem cells and adult stem cells are equivalent in their potential to generate cells of different tissues and organs, both show considerable promise for repairing damaged or defective tissues. In addition, it may be possible for stem cells to deliver genes to specific tissues of the body.
There are numerous questions about stem cells, including their immunologic potential. It is possible that stem cells express immunogenic antigens (markers on the surface of cells) that create a strong immune response in the recipient. Genetically-modified stem cells used in gene therapy may in turn express novel antigens not previously present in the recipient. Immune responses could thus eliminate or reduce the potential benefit of stem cell therapy.
Therefore, there are a number of critical questions related to the immunology of stem cells:
1. Do embryonic/adult stem cells generate an immune response and if so, what antigenic determinants (components of the stem cell surface that are involved in the immune response) are responsible?
2. How does expression of antigens change with differentiation of cells into various tissues and organs?
3. Do specific culture conditions or the specific stem cell source affect immune recognition?
4. Are there methods for altering immune recognition?
5. Are there strategies for stopping the immune response in autoimmune diseases (diseases where a person’s immune system attacks his/her own cells) requiring stem cell therapy?
6. Can allogeneic stem cells (cells that have a different genetic make-up from the recipient) induce tolerance?