ACUTE EFFECTS OF CONTINUOUS INFUSIONS OF HUMAN RECOMBINANT INTERLEUKIN-2 ON SERUM THYROID-HORMONE CONCENTRATIONS IN DOGS

The effect of human recombinant interleukin-2 (IL-2) on serum thyroid hormone concentrations in dogs was studied. Four normal adult dogs rec eived two consecutive weekly cycles of continuous infusions of 3 x 10( 6) U m(-2) daily for four days per week (days 1 to 4 and 8 to 11). The serum concentrations of IL-2, thyroxine (T4) and 3, 5, 3'- triiodothy ronine (T3) were measured before and on days 2, 3 and 4, and 9, 10 and 11 of the infusions. There was a significant decrease in the mean ser um concentrations of T4 and T3 at all times during the infusion of IL- 2; the serum T4 concentrations decreased by 50 to 75 per cent and seru m T3 by 70 to 80 per cent of the pretreatment concentrations in all th e dogs. No antithyroglobulin antibodies were detected in the serum of any of the dogs on days 10 and 11 of the infusions. The concentrations of circulating thyroid hormones decreased rapidly in the dogs during the infusion of IL-2, as in the euthyroid sick syndrome.