Interleukin-1 Beta (IL-1β) Binds to Intact Porcine Thyroid Follicles, Decreases Iodide Uptake but has no Effect on cAMP Formation or Proliferation

Summary Interleukin-1 beta (IL-1β) is known to be involved in autoimmune thyroiditis. Since the results of different in vitro-studies on the effect of IL-1 on thyrocytes are controversial, our aim was to investigate the existence of specific binding sites for IL-1β and its influence on specific functions and growth of isolated porcine thyroid follicles ex vivo with a preserved iodide metabolism. For binding studies isolated thyroid follicles were incubated with 125 I-IL-1β (213.5 nCi/ml) and with increasing concentrations of unlabelled IL-1β (0.06-11.5 nmol/l) for 24h at 4°C. The dissociation constant K d was 0.85 × 10 -10 mol/l and about 800 binding sites per cell were calculated. IL-1β (l0U/ml) decreased basal and TSH-stimulated iodide uptake and organification after an incubation time of 45 min to 6h without any influence on cAMP-formation. In addition, after 40h of incubation IL-1β dose-dependently increased T 3 -secretion, followed by a decrease during simultaneous TSH-stimulation, whereas there was no effect on T 4 -secretion. In contrast to these functional effects IL-1β showed no influence on the growth of thyroid follicles, so that the cytokine cannot be made responsible for goiter growth in thyroid diseases by directly influencing thyroxytes.