Study on induction of immunotolerance against Graves' disease in neonatal mice

Abstract

Objective To investigate the feasibility of inducing neonatal immunotolerance against Graves'disease by gene TSH receptor (TSHR) 289 and its possible mechanism.Methods Neonatal (0-24 h) female BALB/c mice were divided into intraperitoneal injection group,intramuscular injection group,model group,and normal control group.The intraperitoneal group and the intramuscular group were further divided into low-dosage,middle-dosage,high-dosage tolerance groups,and the coresponding control groups.The tolerance groups and the controls were intraperitoneally or intramuscularly pretreated with low-dosage( 1×106 particles),middle-dosage( 1 × 108particles),high-dosage( 1 × 1010 particles)of Ad-TSHR 289 or Ad-lacz respectively.6 to 7 weeks later,the normal control group received intramuscular injection with Ad-lacz; the other groups were immunized with Ad-TSHR289,three times at 3 weeks interval.10 days after the first immunization,serum TRAb was detected.4 weeks after the last immunization,serum TRAb,TT4,splenic CD4 + CD25 + Foxp3/CD4 + were tested,and the thyroid tissues were examinated histologically.Results Ten days after the first immunization,no antibody response against TSHR was detected in the two high-dose tolerance groups,but the TRAb titer in respective controls was significantly higher( P＜0.05 ).4 weeks after the last injection,in high-dose tolerance groups,only 1/10 of mice immunized by intraperitoneal or intramuscular injection elicited anti-TSHR antibody,and no mice immunized intraperitoneally had elevated serum TT4.Two of ten mice challenged intramuscularly showed slightly increased TT4 levels,but the respective controls displayed a strong antibody response( P＜0.01 ) and elevated TT4 level ( P＜0.05 ).The similar percentages of high TT4 and thyroid hyperplasia were found in all groups.Additionally,the frequencies of CD4+CD25 +Foxp3/CD4+in two high-dose tolerance groups were significantly increased as compared to those in controls( P＜0.05 ).The incidence of Graves' disease in the other groups by intraperitoneal or intranuscular injections was not statistically different from those in the corresponding control groups and the model group.Conclusions The immune tolerance against Graves'disease is induced in neonatal mice by either intraperitoneal or intramuscular pathway with specific antigen of TSHR 289,carried by adenovirus vector,and then inhibits Graves' disease in adults. Stimulation with the high-dosage antigen is liable to induce immune unresponsiveness.CD4 + CD25 + Foxp3 +T cells may play an important role in the induction and maintenance of tolerance. Key words: Graves' disease; Animal model; Mice; Immunotolerance