Induction of E‐Rosette‐Promoting Factor in Human Plasma by Levamisole: An Assessment in a Patient with Partial DiGeorge Syndrome

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Abstract
A male infant with partial DiGeorge syndrome responded to weekly administration of levamisole (2.5 mg/kg of body weight) with an increase of circulating E‐rosette‐forming T cells. Thymic hormone activity in plasma appeared to be elevated to a near‐normal level of 11.6 ng thymopoietin equivalent/ml after levamisole administration. The in vitro incubation studies indicated that levamisole by itself had no E‐rosette‐promoting ability, but a dialysable and relatively heat‐stable plasma factor induced by levamisole both in the patient and in heallhy individuals had E‐rosette‐promoting activity for the patient's lymphocytes. Such a plasma factor, however, could not be induced in all four thymectomized myasthenic subjects examined, suggesting a thymus‐dependent nature of the plasma factor. These results suggest that levamisole might mediate an increased secretion of humoral factor(s) with E‐rosette‐promoting activity, even from such a rudimentary thymus as in the partial DiGeorge syndrome.