FOXP3 and Autoimmunity: However, unlike Foxp3 mutations, the T lymphocyte defect is not intrinsic to lymphoid progenitors, as hematopoietic progenitors from normal marrow donors transplanted into Aire-deficient recipients still resulted in autoimmunity, thus establishing that the defective thymic microenvironment, and the absence of Aire expression in mTEC, which underlies the autoimmune phenotype.