Immunity as a function of the unicellular state: implications of emerging genomic data.

Instead of being greeted as supporting the growing corpus of immunological theory, recent advances in the bioinformatic analysis of genomes have often surprised the discoverers and failed to attract the attention of immunologists. In fact, the view that multicellular immune systems are adaptations of already highly evolved unicellular immune systems that are capable of self/not-self discrimination can assist our comprehension of phenomena, such as 'junk' DNA, genetic polymorphism and the ubiquity of repetitive elements. For instance, the 'hidden transcriptome', revealed by run-on transcription of genes or repetitive elements, contains a diverse repertoire of RNA 'immune receptors' with the potential to form double-stranded RNA with viral RNA 'antigens', thus triggering intracellular alarms.