A method for promoting a sustained increased level of T-cell production in immunocompromised subjects in which method enkephalin peptides are administered according to an intermittent dose schedule. In particular, the method involves treatment of immunocompromised patients which includes the administration of enkephalin, either alone or in conjunction with other therapies, in an initial dosage regimen, with periodic booster dosages of enkephalin as necessary to maintain sustained immune system response.