Matthew Hoy
By Matthew Hoy on June 18, 2002

It appears that I was misled on the previous item due to poor reporting. (*Takes the editor and reporter of the piece out back and beats them.*)

Instapundit's Glenn Reynolds got the following e-mail earlier today:

Dr. Steve White of the University of Chicago sent this:

The researchers collected thymic stem cells from mice, not humans (the clonal populations were collected from 15.5 day old mouse embryos). The exact populations were R1 (CD45.MHC class II.MTS24-) and R2 (CD45.MHC class II.MTS24+) cells. These cells were separated from other cells by flow cytometry and then engrafted into mouse kidneys. Embryonic cells at 15.5 days old (mid gestation for a mouse) were used as it was felt that this represented a point at which thymus cells (technically, thymic epithelial cells) had differentiated into two component types for the developing thymus gland.

This is a remarkable study and deserved publication in Nature Immunology. But these were mouse cells, not human cells, and came from an embryo, not an adult. Hope this clarifies it for you.

Dr. White was kind enough to send me the PDF of the Nature article, and he's right -- it says rather clearly in the methodology section that mouse cells, not human cells, were involved.

So, Dr. White has cleared up the particulars of this experiment, but I stand by my contention that this is better news for cloning opponents than it is for cloning supporters.

Note that scientists got these cells from a mouse at "mid-gestation" -- 15 1/2 days for a mouse. Translate that to a similar level of embryonic development in humans and you get 4 1/2 months. I know of no reasonable person who would support destroying human embryos at that stage of development in order to harvest stem cells. If that is the level of fetal development that is required to get usable cells, we can just halt the debate right now -- it's not going to happen.

The other thing about Dr. White's explanation that is notable is "this represented a point at which thymus cells . . . had differentiated into two component types for the developing thymus gland." Note that the cells that were harvested were no longer undifferentiated (or raw) stem cells that embryonic stem cell researchers claim are so beneficial. Instead, while still embryonic stem cells, they appear to be much more similar to the developed adult stem cells about which there is no controversy.


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June 2002



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