Pathogenicity of a human thyroglobulin peptide (2340-2359) in mice with high or low genetic susceptibility to thyroiditis.

We have previously identified a 20-mer peptide of human thyroglobulin (hTg), p2340 (aa2340-2359), which induced experimental autoimmune thyroiditis (EAT) in AKR/J (H-2(k)) and HLA-DR3 transgenic mice. In this study, we investigated the thyroiditogenic potential of p2340 in 'high responder' CBA/J (H-2(k)) and SJL/J (H-2(s)) or 'low responder' C57BL/6 (H-2(b)) and BALB/c (H-2(d)) mice. Mice were immunized subcutaneously with 100 nmol of p2340 in complete Freund's adjuvant (CFA) and both the proliferative capacity of their lymph node cells in the presence of p2340 or intact Tg and the production of peptide-specific antibodies were investigated. The p2340 peptide was found to contain B-cell and non-dominant T-cell epitope(s) in all strains tested. Moreover, it elicited EAT in CBA/J (2/6, infiltration index (I.I.) 1) and SJL/J (5/5, I.I. 1-3) mice after direct challenge and in BALB/c (4/7, I.I. 1) and C57BL/6 (1/5, I.I. 1) after adoptive transfer of p2340-primed lymph node cells. P2340 is the first Tg peptide found to be pathogenic in low as well as high responder mouse strains and thus will allow us to investigate mechanisms of EAT induction in a genetically resistant host.

Human thyroglobulin peptide p2340 induces autoimmune thyroiditis in HLA-DR3 transgenic mice.

In a previous study we demonstrated that the human thyroglobulin (hTg) peptide p2340 (aa 2340-2359) can stimulate a T cell response and elicit experimental autoimmune thyroiditis (EAT) in AKR/J (H-2(k)) mice. In the present study we examined whether p2340 can induce EAT in single HLA class II DR3 transgenic mice. This peptide was found to be immunogenic at the T cell level in DR3 mice, since it induced specific proliferative responses, as well as IL-2 and IFN-gamma secretion in secondary cultures of peptide-primed lymph node cells (LNC). Immunization of HLA-DR3 mice with p2340 in CFA elicited EAT (infiltration index of 1 to 2) in eight of nine mice. Peptide-primed LNC responded to intact hTg, whereas, hTg-primed LNC did not respond to p2340 in culture, suggesting that p2340 contains subdominant T cell epitope(s). P2340 was also found to be immunogenic at the B cell level, since strong p2340-specific IgG response was detected in all transgenic mice tested. Thus, we provide evidence for a pathogenic role of an hTg peptide in HLA-DR3 transgenic mice. Therefore, p2340 could be presented by DR3 molecule in patients with Hashimoto's thyroiditis and participate in the development of the disease.

Induction of murine thyroiditis by a non dominant E(k)-restricted peptide of human thyroglobulin.

We have previously shown that the human thyroglobulin (hTg) 20-mer peptide p2340 (aa 2340-2359) contains an epitope recognized by Tg-reactive B cells in patients with Graves' disease. The presence of several Ek-binding motifs within p2340 prompted us to examine whether this peptide can stimulate a T-cell response and elicit experimental autoimmune thyroiditis (EAT) in AKR/J (H-2k) mice. The peptide was found to be immunogenic at the T-cell level since it induced specific proliferative responses as well as interleukin-2 and interferon-gamma secretion in secondary cultures of peptide-primed lymph node cells (LNC). The p2340-specific proliferation was blocked almost completely by an Ek-specific monoclonal antibody (mAb) but was unaffected by a control Ak-specific mAb. Peptide-primed LNC did not respond to intact hTg and conversely, LNC primed in vivo with hTg did not respond to p2340 in culture, suggesting that p2340 contains non-dominant T-cell epitope(s). Direct subcutanaeous challenge of AKR/J mice (n = 9) with p2340 in adjuvant, elicited mild to moderate EAT (infiltration index of 1-2) and strong p2340-specific immunoglobulin G responses in all mice tested. These data delineate a new thyroiditogenic sequence within the carboxyl terminal region of hTg.