BioBreeding/Worcester (BB/Wor) rats are deficient in the generation of functional cytotoxic T cells.

The BioBreeding/Worcester (BB/Wor) rat provides a good model of spontaneous autoimmune diabetes. There are several sublines of the BB/Wor rat. The diabetes prone (DP) sublines develop diabetes at a frequency of 50 to 80% from 60 to 120 days of age. The DP rats are lymphopenic, have a severe deficit in phenotypic OX 19+ OX 8+ cytotoxic T cells (Tc), and lack RT 6.1 T cells. These rats have a relative increase in OX 19- OX 8+ natural killer (NK) cells and in NK activity as compared with the diabetes resistant (DR) sublines. The DR sublines have a normal complement of phenotypic Tc and RT 6.1 T cells, fewer NK cells, and lower NK activity than the DP rat. The ability to elicit functional Tc in the BB/Wor rat has not been well studied. In these experiments, by using a model of lymphocytic choriomeningitis virus (LCMV) infection in DP and DR rats, we have studied the functional activity of Tc in these lines. Seven days after infection with LCMV, DR rats develop lymphocytes which are cytotoxic for LCMV-infected syngeneic fibroblasts. These cytotoxic lymphocytes are phenotypic Tc (OX 19+ OX 8+), and do not kill Pichinde virus-infected syngeneic fibroblasts or LCMV-infected allogeneic fibroblasts. This cytotoxic activity is accompanied by an increase in phenotypic Tc from 17 to 33%. DP rats produced neither functional nor phenotypic Tc. These studies confirm that NK cells are the predominant cytotoxic lymphocyte in the BB/Wor rat and suggest that these rats may not utilize a Tc mechanism in islet destruction or another immunologic process such as graft rejection.