Thymic extracellular matrix in Down's syndrome.

Down's syndrome (DS) is associated with cellular and humoral immunological abnormalities, and altered histology of the lymphoid and epithelial compartments of the thymus has been reported. In the present study, we investigated the extracellular matrix (ECM) of six DS thymuses. A novel fibroblast-containing network was demonstrated in the cortical region with anti-fibronectin, anti-type I collagen and anti-type IV collagen antibodies. Rupture sites of the basement membrane were also observed. Since the ECM is essential to normal thymic ontogeny, it is likely that the severe intrathymic ECM structure changes occurring in DS may be linked to abnormal cortical thymocyte depletion.