P2RY2 and infection: KC levels increased to a peak value at day 9 post-infection in P2Y2−/− mice whereas in P2Y2+/+ mice the level decreased and was significantly lower at day 9 and day 10 (144.6±24.84 N = 13 vs. 84.91±9.918 N = 19 pg/mL, Fig. 3A).