[Ozone and the immune system]

This review focuses on the effect on health of changes in the immune system secondary to ozone exposure and on various mechanistic hypotheses put forward. Beyond the problems related to the variability of study criteria (e.g. age, sex, concentration and duration of different types of exposure, the slightly volatile nature of ozone and the complexity of the immune system), ozone may induce immunostimulation as shown by intensified allergic phenomena or immunosuppression expressed by increased sensitivity to bacterial infections. Different functions of the immune response (for example macrophage and polynuclear phagocytic and bactericidal activity, NK activity, cytokine and antibody production ...) are affected. In terms of risk, the consequences of these changes depend on their intensity, their perennial nature and their association with particular genetic characteristics or other forms of external aggression, for example infection. The effect of exposure to a mixture of pollutants with unknown interactions should also be taken into consideration. Finally, the problem of normal but possibly exaggerated immune response to a compound whose allergenicity may have been modified by ozone must also be taken into account.