A genomic view of helper T cell subsets.

Genomic-scale gene expression profiling in combination with the availability of a draft sequence of the human genome is beginning to revolutionize the way immunology is done. The possibility of measuring levels of gene expression for tens of thousands of genes simultaneously and in a quantitative fashion aids in the definition of a comprehensive molecular phenotype of cells and cellular processes of the immune system in health and disease. T helper lymphocytes are an essential element of appropriate immune responses to pathogens. To achieve effective immunity, T helper cells differentiate into at least two specialized subsets that direct type 1 and type 2 immune responses. Here, I discuss recent progress that has been made in our understanding of the genetic program that controls the development and functional properties of helper T cell subsets.