THY1 and infection: A preferential expansion of splenic Thy1+ NK cells was also observed, albeit to a lesser degree (approximately 2–fold expansion in the total number of splenic NK cells, and a 5-fold expansion in the number of Thy1+ splenic NK cells; the percentage of total splenic NK cells that were Thy1+ rose from a baseline of 32% to a peak of 57% by 4 days post-infection; data not shown).