New research reveals how some drugs can inadvertently target the immune system, making the body’s own tissues look like foreign invaders. The immune system then attacks the unfamiliar tissues as if they were incompatible transplants. The discovery could lead to the development of a diagnostic test to determine drug hypersensitivity, researchers say. A new study published in the journal Nature shows the biological mechanisms by which a person’s exact tissue type determines whether they will develop the drug allergy or not. This is a significant discovery uncovering the molecular basis of a group of drug hypersensitivities, says Professor James McCluskey of the Department of Microbiology and Immunology at the University of Melbourne. “A whole class of drug allergy is likely to be explained by this discovery,” he says. “There are several drugs that can cause life threatening skin rashes and other symptoms such as fever, diarrhea, muscle aches, and pains. “A simple blood test may help to predict adverse reactions in the treatment of a broad range of conditions like AIDS, epilepsy, gout, and infections.” The study was conducted by PhD student Patricia Illing of the Department of Microbiology and Immunology, who used a combination of cellular immunology, mass spectrometry, and structural biology at the Australian Synchrotron to define the changes in how the immune system recognized the body’s own tissue, in human samples. The next step was to prove this mechanism in other drug allergies linked to an individual’s tissue type and to establish testing of patients prior to receiving drugs to avoid the drug reactions. McCluskey led the study with Professor Tony Purcell from the University of Melbourne’s Bio21 Institute and Professor Jamie Rossjohn from Monash University. The study was done in collaboration with the Queensland Institute for Medical Research and was supported by the Australian Research Council and the National Health and Medical Research Council of Australia.