CD4 and allergic disease: Since Treg functional (i.e., suppressive) properties are more likely to prove informative regarding Treg maturation status and/or the risk for future allergy development, we performed an assay based on cocultivation of magnetically isolated Treg with magnetically isolated non-Treg CD4+ T cells (Tconv) at a 1:5 Treg/Tconv ratio.