Recapitulation of normal and abnormal BioBreeding rat T cell development in adult thymus organ culture

Congenitally lymphopenic diabetes-prone (DP) BioBreeding (BB) rats develop spontaneous T cell-dependent autoimmunity, Coisogenic diabetes-resistant (D R) BE rats are not lymphopenic and are free of spontaneous autoimmune disea se, but become diabetic in response to depletion of RT6(+) T cells. The bas is for the predisposition to autoimmunity in BE rats is unknown. Abnormal T cell development in DP-BB rats can be detected intrathymically, and thymoc ytes from DR-BE rats adoptively transfer diabetes, The mechanisms underlyin g these T cell developmental abnormalities are not known. To study these pr ocesses, we established adult thymus organ cultures (ATOC), We report that cultured DR- and DP-BB rat thymi generate mature CD4 and CD8 single-positiv e cells with up-regulated TCRs, DR-BE rat cultures also generate T cells th at express RT6. In contrast, DP-BB rat cultures generate fewer CD4(+), CD8( +), and RT6(+) T cells. Analysis of the cells obtained from ATOC suggested that the failure of cultured DP-BB rat thymi to generate T cells with a mat ure phenotype is due in part to an increased rate of apoptosis. Consistent with this inference, we observed that addition of the general caspase inhib itor Z-VAD-FMK substantially increases the number of both mature and immatu re T cells produced by DP-BB rat ATOC, We conclude that cultured DR-BE and DP-BB rat thymi, respectively, recapitulate the normal and abnormal T cell developmental kinetics and phenotypes observed in these animals in vivo. Su ch cultures should facilitate identification of the underlying pathological processes that lead to immune dysfunction and autoimmunity in BB rats.