The immune system and gene expression microarrays--new answers to old questions

The recent increase in availability of gene expression technologies has the potential to dramatically expand our understanding of cellular immunology in molecular detail. Expression levels of tens of thousands of genes can be measured in dozens of samples in only a few days, and this data can be integrated with sequence informatics to tentatively assign some (limited) functional information to a majority of these genes. In this review we discuss some initial applications of these new tools to the fields of lymphocyte and monocyte differentiation pathways, the tolerance or immunity decision process, and B cell transformation. These examples illustrate the power of unbiased, 'wide-net', approaches both to drive immunological research in previously unexpected directions and to confirm classic tenets of immunology.