AN IMMUNOHISTOCHEMICAL STUDY ON ORGANIZED LYMPHOID-CELL INFILTRATES IN FETAL AND NEONATAL PANCREASES - A COMPARISON WITH SIMILAR INFILTRATES FOUND IN THE PANCREAS OF A DIABETIC INFANT

Lymphoid cell infiltrates were analyzed using immunohistochemical tech niques on 5 normal fetal and 6 normal neonatal pancreases. Data were c ompared to data obtained analyzing the lymphoid cell infiltrates in th e pancreas of an 8 months old diabetic infant. In the normal fetal and neonatal pancreases islets were intact and not infiltrated. In the di abetic infant beta-cells had vanished in almost all islets, the remain ing islets showed a minor infiltration with primarily T-cells, a few B -cells, and some classical marcrophages. It appeared that a widespread infiltration of the exocrine pancreas with single dendritic-like cell s, and T-cells, and little clusters of these cells were normal feature s of fetal and neonatal pancreases. In the diabetic case these infiltr ative patterns were more pronounced. Larger accumulations of such lymp hoid cells could also be detected in the normal fetal and neonatal pan creases and these consisted mainly of T-cell zones, sometimes containi ng HEV's, with intermingled interdigitating dendritic cells and a few macrophages. This architecture is reminiscent of peripheral lymphoid t issue, such as bronchus-or gut-associated lymphoid tissue. The functio n of this fetal/neonatal intrapancreatic lymphoid tissue (which disapp ears in later life) is unknown. Various possibilities are suggested su ch as a yet unknown ubiquitous fetal/neonatal microbial infection, tol erance induction towards islet cell antigens, an endocrine regulatory function of infiltrated lymphoid cells, and a normal ontogenetic proce ss.