Altered MHC class I expression: a role for transplantation and IDDM autoimmunity

Differences in Suppressor of Cytokine Signaling-1 (SOCS-1) Expressing Islet Allograft Destruction in Normal BALB/c and Spontaneously-Diabetic NOD Recipient Mice

BACKGROUND

The ability to block interferon signaling represents an important strategy in designing therapies to prevent beta-cell destruction during islet allograft rejection.

METHODS

The SOCS proteins regulate cytokine signaling by blocking activation of JAK/STAT proteins. Using islets isolated from SOCS-1 transgenic mice (SOCS-1-Tg; these mice express SOCS-1 under the control of the human insulin promoter and are on the C57BL6/J background), we investigated whether SOCS proteins can prevent the destruction pancreatic islet cells transplanted beneath the kidney capsule of major histocompatibility complex mismatched normal BALB/c and spontaneously-diabetic NOD mouse recipients.

RESULTS

Immunohistochemical staining for insulin confirmed the presence of donor SOCS-1-Tg islets in islet allografts harvested at 22 days posttransplant, whereas grafts of control non-Tg islets were destroyed by 14 days. In contrast, SOCS-1-Tg allogeneic islets were not protected from beta-cell destruction in clinically diabetic NOD mice. The islet allografts functioned for 1 week posttransplant; however, hyperglycemia returned after 2 weeks and the grafts were destroyed. Rejection of SOCS-1-Tg and non-Tg islets in autoimmune diabetic NOD mice was associated with an infiltrate of both CD4+ and CD8+ T cells and a T2-type cytokine response (IL-4) rather than the conventional T1-type cytokine response observed during islet allograft rejection. Self-antigen upregulation in response to IFN-gamma stimulation did not appear to be a factor in rejection of the islet allografts.

CONCLUSIONS

These results demonstrate that expression of SOCS-1 in islets delays islet allograft rejection but cannot circumvent destruction of the islets by the recurrence of the tissue-specific autoimmune process of spontaneous diabetes.

Type 1 diabetes: the facts fit a deficient inhibitory signal given by MHC class II

This paper presents a hypothesis regarding the aetiology of Type 1 (autoimmune) diabetes, which suggests that autoimmunity is normally prevented by an inhibitory or negative signal delivered by MHC molecules, and that in Type 1 diabetes it is the inability of beta cells to deliver sufficient negative signal from MHC Class II that drives the underlying autoimmune process. Based on a broad survey of the diabetes literature, a list of clinical, pathological, experimental and epidemiological 'facts' about Type 1 diabetes is presented which are considered to be widely accepted as proven. The new theory is then compared to other recent theories on the aetiology of diabetes with regard to its ability to explain these accepted 'facts'.