Macrophages and dendritic cells are important as antigen-presenting ce
lls in the islet autoimmune response. We report decreased maturation o
f dendritic cells from blood monocytes of 61 patients with type 1 diab
etes compared with 31 healthy controls (medians 26 and 35%, respective
ly, p=0.0005). The dendritic cells also had reduced ability to cluster
(96 and 124 clusters, respectively, p=0.0005), and to stimulate autol
ogous and allogeneic T cells. Because optimum antigen presentation is
primarily required for tolerance induction rather than for immunisatio
n, the defective maturation and function of diabetic dendritic cells m
ight be the basis for disturbed activation of regulatory (suppressor)
T cells.