I’ve used GFP in a chimera experiment… we made chimeric mouse models from nl B6 mice (recipients) and GFP B6 mice (donors). Our goal was to determine the infiltration of a certain cell population into the CNS of the recipient mice… because GFP is such a bright cell marker, we did not need to tag the cells with fluorescent antibody to determine which were of donor origin. It made the experiment run much quicker, and saved us money in not needing to purchase antibody markers for our target cells. Hope that helped – not sure if that’s the sort of thing you were looking for.