In this image from a study in the Journal of Experimental Medicine, the genome browser screen shot at top shows locations of open chromatin in T cells where transcription factors bind to help the immune cells develop. Color peaks show sites of chromatin opening to facilitate binding. The bottom heat map below shows the presence of the molecule H3K4me2 in the T helper cells of asthma patients and healthy control patients. H3K4me2 is associated with chromatin opening in the nucleus of T helper cells. Researchers looking for improved immune disease treatments report finding a molecular key to the body making healthy T cells.