The decrease in IL-4 production as a result of TET deficiency was apparent even at the first cell division, when most fully methylated DNA in naïve T cells becomes hemi-modified; the decrease became more prominent thereafter, as the fraction of DNA that is fully demethylated on both strands increases to 50% at 2 cell divisions, 75% at 3 divisions, and so on (Additional file 1: Fig. S1N). Here, IL4 is linked to hyperinsulinemic hypoglycemia, familial, 4.