by Despite the presence of numerous infiltrating T cells following B1 cell reconstitution, there appeared to be limited islet cell destruction. pancreas. Second, the infiltrate must convert from an innocuous to an aggressive state, triggering cell destruction and overt diabetes. Several mechanisms are thought to influence the latter checkpoint, including the CTLA-4 pathway (3, 4) and the actions of regulatory T cells (Tregs) (5). However, much less is known about the factors that permit initial tissue entry by autoreactive lymphocytes. Proliferation of autoreactive T cells in the pancreatic lymph node (PanLN) is known Terlipressin to precede pancreas infiltration (6), but it remains unclear whether such priming is sufficient to permit subsequent pancreas entry. Notably, recent data suggest that even preactivated T cells do not constitutively gain entry to nonlymphoid sites and indicate a requirement for local tissue conditioning (7). Although autoimmune diabetes is usually a T cell-driven disease, studies using the NOD mouse (8, 9), the BioBreeding rat (10), and the DO11 RIP-mOVA mouse (11) have shown that B cells, as well as T cells, participate in pancreatic inflammation. Recent data suggest B cells also infiltrate the pancreas in humans with type 1 diabetes (12). Although the requirement for B cells in diabetes is not absolute in mouse (13) or man (14), a large body of evidence suggests an important role for B cells in promoting disease. In particular, pancreas infiltration in B cell-deficient NOD mice has been reported to be virtually absent (15) or significantly suppressed (16). For example, in one study, ~6% of islets were infiltrated in 10- to 12-wk-old B cell-deficient NOD mice, compared with 61% infiltration in age-matched B cell-replete animals (17). Moreover, B cell depletion using anti-IgM has been shown to completely abrogate insulitis in NOD animals (18). Despite clear indications of the importance of B cells, their mechanism of action is still the subject of debate. Islet autoantibodies predict disease onset in both mouse and Terlipressin human (19) but are not thought to be pathogenic in themselves. The elegant demonstration that B cells that are unable to secrete Ab retain the capacity to promote diabetes (20) supports the idea that this role of B cells extends beyond the provision of circulating Ab. In this regard, several studies suggest B cells play an Ag-presenting role in diabetes (17, 21, 22) or support T cell survival within islets (23). New evidence that B cell depletion may be beneficial in humans with type 1 diabetes (24) as well as mice Terlipressin (25, 26) highlights the potential of this subset as a therapeutic target. Rabbit Polyclonal to VEGFR1 (phospho-Tyr1048) Our understanding of the role of B cells in diabetes to date is based on strategies that ablate both conventional B2 cells and the less prevalent B1 cell subset. Thus, the relative contribution of each subset to disease is not clear. In the current study, we have used the DO11 RIP-mOVA mouse model to test the role of B1 cells in diabetes induction. Mice bearing transgenic T cells (DO11.10) specific for a Terlipressin pancreas-expressed protein (OVA) develop spontaneous diabetes. The relatively synchronous disease onset in this model has allowed us to show that B1 cells are present in the pancreas before T cells during the initiation of insulitis. In B cell-deficient transgenic animals, islet-specific T cells fail to enter the pancreas, and this can be reversed by restoring the B1 population by adoptive transfer. These data therefore reveal an unexpected role for B1 cells in policing entry of autoreactive T cells into the pancreas. Materials and Methods Mice DO11.10 TCR transgenic and BALB/c mice were purchased from The Jackson Laboratory (Bar Harbor, ME). RAG2?/? mice were purchased from Taconic Farms (Germantown, NY). Rat insulin promoter (RIP)-mOVA mice on a BALB/c background expressing a membrane-bound form of OVA under the control of the RIP Terlipressin (from line 296-1B) were a gift from W. Heath (Walter and Eliza Hall Institute, Melbourne, Victoria, Australia). Mice were housed at the Birmingham Biomedical Services Unit (Birmingham, U.K.) and used according to institutional guidelines. Blood glucose was measured using an Ascensia Elite XL blood glucose meter (Bayer, Pittsburgh, PA). Mice were considered diabetic following two consecutive readings of 250 mg/dl. Flow cytometry Lymphocytes from the pancreas were obtained as described previously (11). Cells were stained with Abs.
