In this regard, when PBMC from a woodchuck with CH were stimulated with WHV peptide WHc97-110 or PMA/ionomycin and then stained with clone IL2R.1 (anti-CD25) or clone H1.2F3 (anti-CD69), the number of CD25-positive cells increased by about 2% after exposure to the WHV peptide, while that of CD69 reactive cells remained unchanged comparing to unstimulated controls. This evidence concerns the gene CD69 and cyclic hematopoiesis.