Fetal thymus transplantations in severe combined immunodeficiency.

Two brothers with severe combined immunodeficiency were treated with repeated transplantations of fetal thymus tissue. The first patient was not treated until he was critically ill, and the intramuscular transplants had no effect. He died at 11 months of age of overwhelming pneumonia. At postmortem examination a transplanted thymus seemed viable. In the second patient an intramuscular transplant had no effect, but three subsequent intraperitoneal transplants led to transient increase in circulating T lymphocytes with a concomitant fall in B lymphocytes. The results suggested an additive effect of each transplant. However, delayed hypersensitivity skin tests and in vitro mitogen responses were not influenced. Initially, transfer factor was given, and fetal liver was administered intraperitoneally together with the last thymic transplant. Neither of these measures had any observed effect, and this patient, similarly, died of pneumonia at nearly 12 months of age.