Low-density cells isolated from the rat thymus resemble branched cortical macrophages and have a reduced capability of rescuing double-positive thymocytes from apoptosis in the BB-DP rat.

Biobreeding-diabetes prone (BB-DP) rats spontaneously develop organ-specific autoimmunity and are severely lymphopenic and particularly deficient in ART2+ regulatory T cells. A special breed, the so-called BB-diabetic-resistant (DR) rats, are not lymphopenic and do not develop organ-specific autoimmunity. The genetic difference between both strains is the lymphopenia (lyp) gene. Intrathymic tolerance mechanisms are important to prevent autoimmunity, and next to thymus epithelial cells, thymus APC play a prominent part in this tolerance. We here embarked on a study to detect defects in thymus APC of the BB-DP rat and isolated thymus APC using a protocol based on the low-density and nonadherent character of the cells. We used BB-DP, BB-DR, wild-type F344, and F344 rats congenic for the lyp gene-containing region. The isolated thymus, nonadherent, low-density cells appeared to be predominantly ED2+ branched cortical macrophages and not OX62+ thymus medullary and cortico-medullary dendritic cells. Functionally, these ED2+ macrophages were excellent stimulators of T cell proliferation, but it is more important that they rescued double-positive thymocytes from apoptosis. The isolated thymus ED2+ macrophages of the BB-DP and the F344.lyp/lyp rat exhibited a reduced T cell stimulatory capacity as compared with such cells of nonlymphopenic rats. They had a strongly diminished capability of rescuing thymocytes from apoptosis (also of ART2+ T cells) and showed a reduced Ian5 expression (as lyp/lyp thymocytes do). Our experiments strongly suggest that branched cortical macrophages play a role in positive selection of T cells in the thymus and point to defects in these cells in BB-DP rats

Biobreeding rat islets exhibit reduced antioxidative defense and N-acetyl cysteine treatment delays type 1 diabetes

Islet-level oxidative stress has been proposed as a trigger for type 1 diabetes (T1D), and release of cytokines by infiltrating immune cells further elevates reactive oxygen species (ROS), exacerbating beta cell duress. To identify genes/mechanisms involved with diabeto-genesis at the beta cell level, gene expression profiling and targeted follow-up studies were used to investigate islet activity in the biobreeding (BB) rat. Forty-day-old spontaneously diabetic lymphopenic BB DRlyp/lyp rats (before T cell insulitis) as well as nondiabetic BB DR+/+ rats, nondiabetic but lymphopenic F344lyp/lyp rats, and healthy Fischer (F344) rats were examined. Gene expression profiles of BB rat islets were highly distinct from F344 islets and under-expressed numerous genes involved in ROS metabolism, including glutathione S-transferase (GST) family members (Gstm2, Gstm4, Gstm7, Gstt1, Gstp1, and Gstk1), superoxide dismutases (Sod2 and Sod3), peroxidases, and peroxiredoxins. This pattern of under-expression was not observed in brain, liver, or muscle. Compared with F344 rats, BB rat pancreata exhibited lower GST protein levels, while plasma GST activity was found significantly lower in BB rats. Systemic administration of the antioxidant N-acetyl cysteine to DRlyp/lyp rats altered abundances of peripheral eosinophils, reduced severity of insulitis, and significantly delayed but did not prevent diabetes onset. We find evidence of b cell dysfunction in BB rats independent of T1D progression, which includes lower expression of genes related to antioxidative defense mechanisms during the pre-onset period that may contribute to overall T1D susceptibility

Bruton's tyrosine kinase (BTK) function is important to the development and expansion of chronic lymphocytic leukemia (CLL)

Chronic Lymphocytic Leukemia (CLL) demonstrates variable reactivity of the B cell receptor (BCR) to antigen ligation, but constitutive pathway activation. Bruton's Tyrosine Kinase (BTK) shows constitutive activity in CLL, and is the target of irreversible inhibition by ibrutinib, an orally bioavailable kinase inhibitor that has shown outstanding activity in CLL. Early clinical results in CLL with other reversible and irreversible BTK inhibitors have been less promising, however, raising the question of whether BTK kinase activity is an important target of ibrutinib and also in CLL. To determine the role of BTK in CLL, we utilized patient samples and the E\u3bc-TCL1 (TCL1) transgenic mouse model of CLL which results in spontaneous leukemia development. Inhibition of BTK in primary human CLL cells by siRNA promotes apoptosis. Inhibition of BTK kinase activity through either targeted genetic inactivation or ibrutinib in the TCL1 mouse significantly delays the development of CLL, demonstrating that BTK is a critical kinase for CLL development and expansion and thus an important target of ibrutinib. Collectively, our data confirm the importance of kinase-functional BTK in CLL