Recovery of immune function after cessation of maintenance therapy in acute lymphoblastic leukemia (ALL) of childhood.

In previously healthy children, serum immunoglobulin levels at diagnosis of acute lymphoblastic leukemia (ALL) were entirely in the normal range. After antileukemic therapy had been given for 26-27 months, serum immunoglobulin levels were low. In 32 children these parameters could be followed for periods up to 3 years after cessation of therapy, the patients remaining in unmaintained remission. At cessation of therapy serum immunoglobulin levels were at the tenth centile of the normal range or slightly below. IgG promptly returned to normal levels and then remained in the normal range. IgA levels were restored much more slowly. Most striking was the slow and incomplete return of serum IgM to normal levels. Even after a follow-up of 3 years the mean was still subnormal. This was not accompanied by clinical signs of disturbed immunity. Our study points out that in assessing the long-term immunosuppressive effects of anticancer therapy the follow-up period must be sufficiently long.