Morphometric evidence for a striking B-cell reduction at the clinical onset of type 1 diabetes.

The distribution and volume of the pancreatic endocrine cells were studied in a case of type 1 diabetes with a duration of approximately 7 days. Immunocytochemical techniques combined with morphometry were used. The PP-cell rich lobe, making up about 10% of the total pancreatic volume, was not included in this study. The volume density and the absolute volume of the B-cells was found to be reduced to about one third to one seventh of the values determined in four controls of similar age and/or pancreatic volume. The A-cell volume was also diminished whereas the D- and PP-cell volume remained constant. As B-cell necroses could not be detected and insulitis was in the initial stages of development it is concluded that the destruction of B-cells proceeds slowly in type 1 diabetes. In the majority of cases it probably starts years before the clinical onset of the disease.