From an article by Tracy S. P. Heng of Harvard Medical School, in Nature Immunology 9, 1091 – 1094 (2008) :
“The genome-sequencing and variation-mapping projects have established essential genetic ‘road maps’. In the same vein, if on a more focused scale, by generating robust expression data and metadata into a centralized and accessible location, the Immunological Genome project should provide an essential ‘workbench’ for delineating the intricate workings of the immunological genome.
Thanks to the broad and robust approaches allowed by gene-expression microarrays and related techniques, the transcriptome is probably the only ‘-ome’ that can be reliably tackled in its entirety. Generating a complete perspective of gene expression in the immune system offers the potential for deciphering patterns that mirror responses at several levels. At the level of the gene, such data can give insight into how individual genes act along differentiation profiles and cellular responses. It is then possible to define modules or groups of genes whose expression is interdependent and is coordinated by shared regulatory controls. Computational methods for reverse engineering can then be applied to infer a model of the cells’ underlying control system. Finally, genome-wide expression data at the highest level of integration provides an objective definition of the relations and distinctions between cells. For example, analyses of relative ‘distances’ in genomic space have shown that natural killer T cells are actually a subset of conventional CD4+ T cells and not an ‘intermediate’ between CD4+ T cells and natural killer cells, as is often believed. Thus, insights from genomic profiling may ‘fine tune’ or revise the classifications and mental representations of immune cells."