It's a hard question to answer, because what we need is not so much the raw number of donors, we need to have donors who are available to donate. We prefer to use male donors. We prefer to use young male donors. And we need to have donors who are of a mixed ethnic heritage, or of our ethnic minorities, to increase the odds that a given donor is going to be a good immune match.
So it's not the absolute number that we need; it's a subset to target those for whom we have trouble finding donors. There is no absolute number on that.