B-CELL-ADHERENT SPLENOCYTES PRECEDE THE ONSET OF DIABETES IN LOW-DOSE STREPTOZOTOCIN-TREATED MICE

Splenocytes from low-dose (40 mg·kg-1 day-1) streptozotocin-treated mice were tested for their binding ability to rat insulinoma (RINm-5F) cells in a rosette-forming cell assay, before and during the onset of diabetes. They displayed a higher (p<0.0001) RIN-adherence than control splenocytes. Such an enhanced binding of splenocytes from diabetic mice was observed on another B-cell (HIT cell) line, but not on non-B cells (particularly on exocrine pancreatic cells, endocrine cells or natural killer-target cells), suggesting that the increased RIN-binding is B-cell specific. This B-cell specificity was also suggested by the use of increasing splenocytes/RIN ratios showing a saturation of RIN-binding in streptozotocin-treated mice. Depletion of lymphocyte subsets revealed that supernumerary RIN-adherent splenocytes from diabetic mice were mainly T lymphocytes, involving both L3T4+ and Lyt2+ cells. Overall, the increased splenocyte-RIN binding was concomitant with the occurrence of islet destruction, but preceded the onset of hyperglycaemia by five days and even the islet immune infiltration. An increased number of RIN-binding splenocytes was also found in mice treated with 33 mg·kg-1·day-1 of streptozotocin, displaying insulitis but not hyperglycaemia. This phenomenon was not found with splenocytes from mice displaying a "toxic" diabetes induced by a single high dose of streptozotocin. No correlation could thus be found between numbers of RIN-binding splenocytes and blood glucose levels, indicating that this phenomenon was not due to metabolic disturbances. These data describe a new marker of cellular immunity in this animal model. This marker is detectable before the clinical onset of diabetes and is more closely linked to insulitis than to hyperglycaemia. © 1990 Springer-Verlag.