FOXP3 and Autoimmunity: Thus, the underlying cause promoting the occurrence of spontaneous deaths from an age of > 7 weeks onwards has remained less clear but may involve the exacerbation of chronic, low-level inflammation in individual organs, such as the thyroid gland or the lungs (Figure 4A), rather than multi-organ autoimmunity observed in Foxp3-deficient models of complete Treg cell deficiency.