[Cytokines and allergy]

The immune system is a homeostatic system adaptating the internal self to the variations of the external non-self and allowing us to get on well together with the environment. Intercellular communications are necessary for the system well operating and are mediated by either direct contacts or by soluble factors called cytokines. Allergy is the upshot of a disregulation of the immune response that does not discriminate between a potentially harmful antigen (tetanus toxoid) and a rather harmless antigen (pigeon droppings). This could be the result of an imbalance between two helper T lymphocytes subsets called TH1 and TH2: their main produced cytokines, respectively IFN-gamma and IL-4, have opposite effects on IgE synthesis whereas other cytokines (IL-3, IL-5) are more directly involved in the differentiation of eosinophil and mast cells lineages.