January 14, 2012
Stem Cell Reports and Asking questions.
There are a number of headlines about stem cells as a cure for type 1 that have been written in the past few days. They are based on a study out of China the reports to have reeducated lymphocytes aka T cells. I read this article and am left with far more questions than I am comfortable with. Josh Levy has a sound write up, I recommend his write up.
In part here why I have questions. In other news this week identified CD8 T cells as the source of the autoimmune response that causes type 1.1 There is a quote from ViaCyte on Diabetes Mine that spoke to the difficulty of getting stem cells to differentiate into beta cells.2 For that I presume that getting a stem cell to differentiate into any specific cell is an involved proposition.
The lymphocytes reportedly reprogramed in the China study are already differentiated cells. If the autoimmune process is stopped it is due to a modification or reeducation of these CD8 T cells. There are a myriad of CD8 cells and they are created in the lymph nodes to recognize specific antigens on the cells the are programmed to kill.
Differentiated means a stem cell became a specific cell in the body. That is they started off as a stem cell and became a specific type of t cell. Very loosely hematopoietic stem cel in bone marrow become a common lymphoid projenitor that becomes a T cell.
This study suggests that exposure to stem cells changes the existing antigen receptors. If that is true then why don’t the stem cell that become to the lymphocytes in our bone marrow have the same effect? I also fail to see a mechanism to explain how this erase the memory of the adaptive immune system. Why is it the type 1 autoimmune T cells that are reeducated and not say the one that provide immunity to chickenpox.
All that said I would love to see a cure. I get excited by headlines just like everyone else. I hope this is repeatable. I have come to be suspicious of reports of apparatus that seem to good to be true.
I would hope that the news agencies that report this kind of study know enough to ask some basic questions. Among them should be how does it work, is it peer reviewed and has the study been repeated?
1 La Jolla Institute researchers identify pivotal immune cell in Type 1 diabetes in humans, http://www.eurekalert.org/pub_releases/2012-01/ljif-lji011112.php