Insulitis in the pancreas of non-diabetic organ donors under age 25 years with multiple circulating autoantibodies against islet cell antigens

Abstract

Autoantibodies against islet cell antigens are routinely used to identify subjects at increased risk of symptomatic type 1 diabetes, but their relation to the intra-islet pathogenetic process that leads to positivity for these markers is poorly understood. We screened 556 non-diabetic organ donors (3 months to 24 years) for five different autoantibodies and found positivity in 27 subjects, 25 single- and two double autoantibody-positive donors. Histopathological screening of pancreatic tissue samples showed lesion characteristic for recent-onset type 1 diabetes in the two organ donors with a high-risk profile, due to their positivity for multiple autoantibodies and HLA-inferred risk. Inflammatory infiltrates (insulitis) were found in a small fraction of islets (<5%) and consisted predominantly of CD3+CD8+ T-cells. Islets with insulitis were found in close proximity to islets devoid of insulin-positivity; such pseudo-atrophic islets were present in multiple small foci scattered throughout the pancreatic tissue or were found to be distributed with a lobular pattern. Relative beta cell area in both single and multiple autoantibody-positive donors was comparable to that in autoantibody-negative controls. In conclusion, in organ donors under age 25 years, insulitis and pseudo-atrophic islets were restricted to multiple autoantibody-positive individuals allegedly at high risk of developing symptomatic type 1 diabetes, in line with reports in older age groups. These observations may give further insight into the early pathogenetic events that may culminate in clinically overt disease.

Keywords: Autoantibodies; Beta cells; HLA class I; HLA-DQ; Insulitis; Islets; Type 1 diabetes.

Fig. 1

Relative beta cell area (a) and the percentage of replicating beta cells (b) in the pancreas of autoantibody-positive organ donors (n=27) and matched controls (n=27). The two donors with multiple autoantibodies and insulitis are indicated with a green dot (DBB-A096) and a red dot (DBB-3504). Results are expressed as mean (a) or median (b) with individual data points. No significant difference was found between both study groups using an unpaired Student t test (a) or an unpaired Mann-Whitney test (b) at the .05* level

Fig. 2

Immunofluorescent staining of pancreas sections from a 22-year-old male organ donor positive for GADA and ICA autoantibodies (DBB-3504). Staining for insulin (green) and glucagon (red) reveals a lobular area (above the dotted line) (a) containing pseudo-atrophic islets devoid of insulin (b). Immunostaining for the leucocytic marker CD45 (brown) in combination with the pan-endocrine marker synaptophysin (red) showing peri-insulitis (c). Staining for CD3 (green), CD8 (red), and insulin (blue) shows an insulitic lesion consisting of a cluster of predominantly lymphocytic cells in the islet periphery (d)

Fig. 3

Immunofluorescent staining of pancreas sections from a 17-year-old male organ donor positive for IA-2A and ZnT8 autoantibodies (DBB-A096). Staining for insulin (green) and glucagon (red) shows multiple small foci (a) or larger lobular areas of pseudo-atrophic islets (on the right of the dotted line) (b). Insulitic lesions were predominantly found at the islet periphery (c) and show small lymphocytic infiltrates composed of CD3+CD8+ T-lymphocytes (d). Insulin-containing islets show marked positivity for the replication marker Ki67 (e)