Measurement of the concentration of H-2 complex antigens in the surface membrane of mouse pancreatic β3-cetls by a quantitative immunoferritin-labeling technique revealed that the antigens were present in very small amounts on the β3-cells of five strains. Å comparison of the labeling densities in the five strains suggested that β3-cells from C57BL/10Sn congenic strains have about half the H-2 antigen density of BALB/c and C3H/HeJ cells, in C57BL/10Sn mice the antigen density on β3-cells was slightly greater than that on erythrocytes, about 20% of that on thymocytes, and about 2.5% of that present on peritoneal macrophages.
Intraperitoneal allografts of C57BL/10Sn islets were uniformly rejected by B10.BR/SgSn diabetic recipients only when the islets were accompanied by 107 peritoneal lymphoid cells. When transplanted without peritoneal cells, C57BL/10Sn islets were only marginally rejectable. In a group of nine such allografts, three diabetic recipients were permanently cured and three others showed rejection times of about 30 days. Sensitization of the three mice showing permanent cures, using 107 allogeneic peritoneal cells at about 40 days after the transplant, did not cause rejection of the allografts. isogeneic transplantation of cell suspensions from dissociated islets of Langerhans was markedly less effective in controlling diabetes than intact islets, and dissociation did not obviously improve the rate of allograft survival. However, 5/19 diabetic mice receiving allografts of dissociated islet cells showed longterm reversals of diabetes that were unaffected by administration of 107 peritoneal cells at about 100 days after the transplant. Recipient mice whose diabetes was reversed by islet allografts and unaffected by specific sensitization had pancreatic insulin concentrations characteristic of diabetic mice. Our reversals of diabetes with untreated islet allografts may be due to the cleanliness of islet preparations obtained with a modified isolation technique, and to the very low density of H-2 complex antigens on C57BL/10Sn β-cells.