My 11 year old son was diagnosed with type�1 diabetes nearly two and a half years ago, and I have read your reply to a question on saving cord blood for possible future use. There is no possibility of my having any further children, and I wondered how close the relationship of the donor to the recipient would have to be. For example, I have two sisters-in-law on my husband’s side of the family who will be having children in the future. The donor would be a first cousin to my son. Is that likely to produce matching tissue? I also have two older daughters. Would their children produce a closer match for their brother?

I myself am no expert in stem cells, but we do have one in this center, and what I say comes from her. You may perhaps have read a more encouraging report on this subject by another Diabetes Team member which in essence said go ahead and establish a stem cell line in the expectation that present difficulties will soon be resolved.

One of the main advantages of the stem cell approach is of course that it gets around the problem of the lack of islet cell donors. First of all, though cord blood stem cells are what is called mesodermal and can normally be used only to provide other mesodermal tissue such as red and white blood cell precursors where they can be life saving. Pancreatic beta cells would have to come from an endodermal line, and, as matters stand at the present, they cannot be derived from cord blood stem cells, but would have to come from a less differentiated source, embryos. Moreover, the ability to develop insulin-producing stem cells is only in its very earliest stage though it has indeed been very recently achieved.

However, there is another major problem in that stem cells will, by virtue of their ability to synthesise insulin, still be vulnerable to autoimmune attack even though your son’s islets are by now destroyed. One way to get around this would be life time immunosuppression which you have to do with islet cell transplants. Another solution is to establish a bone marrow chimera with a white cell line developed from the same basic stem cell precursor. This would permit tolerance of the insulin producing graft without the need for immunosuppression. All rather complex perhaps; but if you can get hold of a copy of the September 4, 2001 edition of The New York Times, there is a very well written article that describes this idea.

Stem cells also seem less susceptible to conventional rejection so that I don’t think it would matter which cousin was the donor, but at present there would still be the autoimmune problem.

DOB