DiGeorge syndrome

…hereditary, T-cell deficiency disease called DiGeorge syndrome arises from a developmental defect occurring in the fetus that results in the defective development of the thymus. Consequently the infant has either no mature T cells or very few. In the most severe cases—i.e., when no thymus has developed—treatment of DiGeorge syndrome…

For example, two autoimmune diseases, DiGeorge syndrome and Nezelof disease, result in the failure of the thymus to develop and in the subsequent reduction in T-cell numbers, and removal of the bursa from chickens results in a decrease in B-cell counts. The destruction of bone marrow also has devastating effects…