Co-stimulatory signal GL50-ICOS expression in thyroid of Graves＇ disease and its immune pathogenetic significance

Objective To study the expression of co-stimulatory molecules, GL50-ICOS, in thyroid tissue of patients with Graves＇ disease （GD） and to explore their relationship with the immune pathogenesis of GD.Methods RT-PCR, Western blot, immunohistochemistry were applied to detect the expression of GL50-ICOS in thyroid of GD. Thyrocytes were cultured in the absence or presence of pro-inflammatory cytokines. The expression of GL50 on thyroid follicular cells （TFC） was further measured by flow cytometry. Results （1） In GD patients,the percentage of CD4＋ CD28- T cells was significantly increased as compared with the control healthy individuals. The expression of co-stimulatory molecule ICOS was up-regulated. （2） The mRNA level of ICOS was significantly increased in GD patients than that in nontoxic goiter（NTG） patients（P〈0.01）. （3）Compared with NTG control group, the GL50 protein expression was much higher in thyroid tissues of GD patients （P 〈0.01）. （4）The results of immunohistochemistry showed that GL50 expression was observed in all GD thyroid tissues, while no expression of GL50 was detected in NTG thyroid tissues（P〈0. 01）. （5） The expression of GL50on primary cultured thyroid follicular cells was significantly increased under the stimulatation of pro-inflammatory cytokines in vitro. Conclusion GL50-ICOS is expressed abnormally in thyroid tissue of patients with GD. Key words: Costimulatory molecule;  Graves＇ disease;  Thyroid