Chimeric drift in allophenic mice: Analysis of changes in red blood cell and white blood cell populations in C57BL/6 ↔ A mice

Fifteen allophenic mice of the type C57BL/6 ? A were quantitatively analyzed for changes in their peripheral white blood cell composition and hemoglobin composition with age. It was found that $\text{7}\text{15}$ or 47% of the mice showed significant changes, termed “chimeric drift,” in one or the other of these parameters. The seven mice showing chimeric drift were classified as unstable chimeras, as opposed to the eight apparently stable chimeras. Chimeric drift was observed in the direction of either parental type, or back and forth, and was found to be independent of the coat color, age, or sex of the mouse. There was an excellent correlation of peripheral white blood cell and hemoglobin compositions of the stable chimeras. However, the unstable chimeras often showed a marked discordance of these two markers.