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Heterogeneity of islet pathology in two infants with recent onset diabetes mellitus
A Lernmark1, G Klöppel, D Stenger
1Department of Medicine, University of Washington, Seattle 98195.
Insights
The destruction of pancreatic beta cells in insulin-dependent diabetes mellitus (IDDM) involves varied immune cell infiltration, particularly macrophages, suggesting diverse autoimmune destruction pathways. This highlights the complexity of IDDM pathogenesis.
Area of Science:
- Immunology
- Endocrinology
- Pathology
Background:
- The autoimmune destruction of pancreatic beta cells in insulin-dependent diabetes mellitus (IDDM) remains incompletely understood.
- Investigating the pancreatic histopathology and immunopathology in young IDDM patients offers insights into disease mechanisms.
Observation:
- Two young children with IDDM, both HLA-DR 3/4, DQ 2/8 positive, exhibited severe loss of insulin-producing beta cells.
- Both patients displayed significant islet macrophage infiltration (HAM-56 positive), alongside varying degrees of lymphocytic infiltration (insulitis).
- Aberrant HLA class II antigen expression was not observed on beta cells, but HLA-DQ8 was present on endothelial cells.
Findings:
- Despite similar beta cell loss, the extent of insulitis differed between the two patients.
- Glutamic acid decarboxylase immunoreactivity was found in both insulin- and glucagon-producing islet cells.
- Macrophage infiltration was a prominent feature in both cases, irrespective of insulitis severity.
Implications:
- The heterogeneity in insulitis suggests that different dynamics and extents of immune cell involvement may underlie beta cell destruction in IDDM.
- Understanding these varied pathomechanisms is crucial for developing targeted therapies for IDDM.
- Macrophage infiltration may play a significant role in beta cell destruction in IDDM, warranting further investigation.
Abstract:
The mechanisms by which the beta cells of pancreatic islets are destroyed in insulin-dependent diabetes mellitus (IDDM) are poorly understood. In this report the pancreatic histo- and immunopathology of two children, both HLA-DR 3/4, DQ 2/8 positive and who both died from cerebral oedema within a day of clinical diagnosis of IDDM, were investigated. Patient 1, a 14-month-old girl, had a 4-week history of polydipsia and polyuria. Patient 2, a 3-year-old boy, had 2 days of illness. Both patients had a similarly severe loss of insulin cells but differed markedly as to the extent of lymphocytic islet infiltration (insulitis). Apart from insulitis, marked islet macrophage infiltration was demonstrated in both patients with the HAM-56 monoclonal antibody. Neither patient showed aberrant expression of HLA class II antigens on insulin-immunoreactive cells, but allele-specific HLA-DQ8 expression was evident on endothelial cells. Glutamic acid decarboxylase immunoreactivity was detected in both insulin- and glucagon-immunoreactive cells. It is concluded that the heterogeneity of islet pathology, especially insulitis, may reflect different dynamics and extent rather than different pathomechanisms of immune destruction of islets in IDDM.