Drug hypersensitivity reactions result from the activation of the immune system
by drugs or their metabolites. The clinical presentations of drug hypersensitivity can range
from relatively mild local manifestations to severe systemic syndromes that can be lifethreatening.
As in other allergic reactions, the causes are multifactorial as genetic, metabolic
and concomitant factors may influence the occurrence of drug hypersensitivity. Formation of
drug protein adducts is considered a key step in drug adverse reactions, and in particular in
the immunological recognition in drug hypersensitivity reactions. Nevertheless, noncovalent
interactions of drugs with receptors in immune cells or with MHC clefts and/or
exposed peptides can also play an important role. In recent years, development of proteomic
approaches has allowed the identification and characterization of the protein targets for
modification by drugs in vivo and in vitro, the nature of peptides exposed on MHC molecules,
the changes in protein levels induced by drug treatment, and the concomitant modifications
induced by danger signals, thus providing insight into context factors. Nevertheless, given the complexity
and multifactorial nature of drug hypersensitivity reactions, understanding the underlying mechanisms also requires
the integration of knowledge from genomic, metabolomic and clinical studies.