B-Cells Promote Intra-Islet CD8⁺ Cytotoxic T-Cell Survival to Enhance Type 1 Diabetes

Abstract

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.