Defects of pattern recognition: primary immunodeficiencies of the innate immune system

Genetic defects leading to impaired recognition of invading pathogens by the innate immune system, and hence to increased susceptibility to specific classes of microorganisms have been recently recognized. To date, defects have been described in three of the major families of pattern recognition receptors (PRRs): the Toll-like receptors (TLRs), the C-type lectin receptors (CLRs), and the nucleotide binding domain leucine-rich repeat containing receptors (NLRs). By contrast, defects in the viral receptors RigI helicases have not been found. PRR defects vary greatly in severity, display a narrow susceptibility profile towards specific pathogens, and when severe in infancy and childhood, often decrease in severity thereafter. Their discovery leads to crucial insight in the pathophysiology of infections, and offer therapeutic targets for future immunotherapy.