Genomics in the immune system.

The analysis of gene expression in tissues, cells, and biologic systems has evolved in the last decade from the analysis of a selected set of genes to an efficient high throughput whole-genome screening approach of potentially all genes expressed in a tissue or cell sample. Development of sophisticated methodologies such as microarray technology allows an open-ended survey to identify comprehensively the fraction of genes that are differentially expressed between samples and define the samples' unique biology. This discovery-based research provides the opportunity to characterize either new genes with unknown function or genes not previously known to be involved in a biologic process. The latter category may hold surprises that sometimes urge us to redirect our thinking. Here, we review the impact of large-scale gene expression profiling by DNA-microarray technology on basic and clinical aspects of immunology.