OBJECTIVE—To determine the role of B-cells in promoting CD8+ T-cell—mediated β cell destruction in chronically inflamed islets.
RESEARCH DESIGN AND METHODS—RIP-TNFα-NOD mice were crossed to B-cell–deficient NOD mice, and diabetes development was monitored. We used in vitro antigen presentation assays and in vivo administration of bromodeoxyuridine coupled to flow cytometry assays to assess intra-islet T-cell activation in the absence or presence of B-cells. CD4+Foxp3+ activity in the absence or presence of B-cells was tested using in vivo depletion techniques. Cytokine production and apoptosis assays determined the capacity of CD8+ T-cells transform to cytotoxic T-lymphocytes (CTLs) and survive within inflamed islets in the absence or presence of B-cells.
RESULTS—B-cell deficiency significantly delayed diabetes development in chronically inflamed islets. Reintroduction of B-cells incapable of secreting immunoglobulin restored diabetes development. Both CD4+ and CD8+ T-cell activation was unimpaired by B-cell deficiency, and delayed disease was not due to CD4+Foxp3+ T-cell suppression of T-cell responses. Instead, at the CTL transition stage, B-cell deficiency resulted in apoptosis of intra-islet CTLs.
CONCLUSIONS—In inflamed islets, B-cells are central for the efficient intra-islet survival of CTLs, thereby promoting type 1 diabetes development.
- BrdU, bromodeoxyuridine
- CTL, cytotoxic T-lymphocyte
- DC, dendritic cell
- FACS, fluorescence-activated cell sorter
- IFN, interferon
- PLN, pancreatic lymph node
- RIP, rat insulin promoter
- TNF, tumor necrosis factor
- Treg, T regulatory
- Received September 5, 2007.
- Accepted January 4, 2008.