In the Proceedings of the National Academy of Sciences this week, Graham Lord at King's College London has led a study that checked into the genetic factors behind the differentiation of CD4⁺ T helper cells. In searching for target genes of the transcription factors T-bet and GATA-3, which direct the differentiation of Th cells into Th1 and Th2 cells, they created a genomic map of T-bet and GATA-3 binding in primary human T cells.