EFFECT OF INSULIN GROWTH-FACTOR (IGF-1) A ND INSULIN (INS) ON HLA-DR ANTIGEN EXPRESSION IN CULTURED HUMAN THYROCYTES - ANOTHER FACTOR OF THE AUTOIMMUNE PROCESS

The aim of this study was to determine whether IGF-1 and INS are able to induce HLA-DR antigen expression (AgHLA-DR) in cultured human thyro cytes. Cytotoxicity assay in thyroid epithelial cells (cultured for 7 days to avoid spontaneous antigen expression) from 14 patients operate d due to different thyroidal diseases, was used to assess HLA-DR expre ssion. AgHLA-DR was reinduced adding IFN-delta. IGF-1 or INS to the cu lture media, alone, combined or associated with TSH or TBII. Both IGF- 1 and INS induced HLA-DR expression in a similar way as IFN-delta did, and the response was enhanced with their combination, suggesting that they have different sites of action Their association with TSH or TBI I further augmented the response. To determine if IGF-1 acts via lymph ocyte IFN-6 secretion, peripheral lymphocytes from 5 normal subjects w ere cultured with and without IGF-1 and the supernatant was used as st imulator, observing a stimulation similar to that induced by IFN-delta . This finding supports the hypothesis that IGF-1 acts stimulating a s pecific tyrosine kinase protein (p56 lck) which is located in T lympho cyte receptors According to our results we can conclude that. at least in vitro. both IGF-1 and INS play a role in the Immune process, proba bly exerting a paracrine effect on autoimmunity, acting as perpetuatin g factors.