A, With > 90% purity, Car4+/+ and Car4−/− bone marrow–derived eosinophils (EOS, 2×106) were assessed for their cellular pH buffering capacity in saline without IL-5 following repetitive addition of 5 μL of 0.1 M HCl into 1 mL of cell suspension each time, with cell-free saline solution alone as negative control without cellular buffering. B, The intracellular pH changes in Car4+/+ and Car4−/− eosinophils were graphed before and after the exogenous lactate challenge (20 minutes), demonstrating no difference in buffering capacity which is required for lactate transport into cells. (mean ± SEM)