Prevention of spontaneous but not of adoptively transferred diabetes by injection of neonatal BB/hooded hybrid rats with splenocytes or concanavalin A blasts from diabetes-free strains.

Spontaneous diabetes was fully prevented in 65 BB/hooded (BB/h) highly diabetes-prone hybrid rats that were given five intraperitoneal injections (25 to 30 x 10(6) cells/injection) of fresh splenocytes or concanavalin A (ConA)-activated cultured splenocytes (blasts) from the diabetes-free Wistar-Furth or Long-Evans strains during the first 2 postnatal wk. Rats remained under observation for up to the age of 180-200 days. Of 70 littermate controls that received no cell injections, 63 developed overt diabetes before the age of 180 days. One intraperitoneal injection (25 x 10(6) cells) of splenocytes or blasts given during the first 36 h after birth was not as effective as multiple injections in preventing overt diabetes. Mild insulitis was present in 4 of 59 "protected" rats; small, discrete mononuclear infiltrates in periductular connective tissue and/or between pancreatic acini were observed in 27. Nondiabetic BB/h rats that were protected with splenocytes or blasts from diabetes-free strains had the same degree of lymphopenia in peripheral blood and spleen as age-matched, insulin-treated diabetic BB/h rats, but the level of islet cell surface antibodies in their serum was significantly lower. The same neonatal injections that protected rats from the development of spontaneous diabetes were completely ineffective in preventing the adoptive transfer of diabetes later in life by the injection of blasts from acutely diabetic BB/h rats.