Innate immunity and hypersensitivity syndrome

Viral infections are frequently followed by an increased risk of allergic disorders. We have recently demonstrated an intimate relationship between human herpesvirus 6 (HHV-6) reactivation and drug-induced hypersensitivity syndrome (DIHS). Kano et at. have demonstrated that a dramatic decrease in circulating B and NK cells as well as serum immunoglobulin levels was observed in DIHS at the onset but not in controls. Although these alterations returned to normal on full recovery, NK cells in patients with DIHS displayed a defective ability to express CD122 (IL-2/15R beta) even long after recovery. To test the effect of NK cells, we next investigated NK-depletion experiments. A significant increase in HHV-6 DNA was only detected in NK-depleted cultures of PBMC from DIHS patients in the presence of the causative drug. Because gamma delta-T cells play an important role in viral infections, we investigated whether gamma delta-T cells are also important for preventing HHV-6 reactivation. Expansion of gamma delta-T cells was only observed in undepleted cultures of PBMC, not in NK-depleted cultures, from patients in the presence of the causative drug. Thus, cross-talk between NK cells and gamma delta-T cells or B cells would represent a first line of defense against latent virus, such as HHV-6. (c) 2005 Elsevier Ireland Ltd. All rights reserved.