Tertiary Lymphoid Structures in the Pancreas Promote Selection of B Lymphocytes in Autoimmune Diabetes

Abstract

Autoimmune diabetes occurs when invading lymphocytes destroy insulin-producing β cells in pancreatic islets. The role of lymphocytic aggregates at this inflammatory site is not understood. We find that B and T lymphocytes attacking islets in NOD mice organize into lymphoid structures with germinal centers. Analysis of BCR L chain genes was used to investigate selection of B lymphocytes in these tertiary lymphoid structures and in draining pancreatic lymph nodes. The pancreatic repertoire as a whole was found to be highly diverse, with the profile of L chain genes isolated from whole pancreas differing from that observed in regional lymph nodes. A Vκ14 L chain predominated within the complex pancreatic repertoire of NOD mice. Skewing toward Vκ4 genes was observed in the pancreas when the repertoire of NOD mice was restricted using a fixed Ig H chain transgene. Nucleotide sequencing of expressed Vκs identified shared mutations in some sequences consistent with Ag-driven selection and clonal expansion at the site of inflammation. Isolated islets contained oligoclonal B lymphocytes enriched for the germinal center marker GL7 and for sequences containing multiple mutations within CDRs, suggesting local T-B interactions. Together, these findings identify a process that selects B lymphocyte specificities within the pancreas, with further evolution of the selected repertoire at the inflamed site. This interpretation is reinforced by Ag-binding studies showing a large population of insulin-binding B lymphocytes in the pancreas compared with draining lymph nodes.

CD4 T cell differentiation in type 1 diabetes

“…In a second TCR transgenic model, based on a different pancreatic antigen and different transgenic T cells, enriching for T cells with a Tfh phenotype increased their capacity to cause diabetes upon adoptive transfer [106]. Anecdotal evidence also links the Tfh response with diabetes in NOD mice: the spontaneous formation of germinal centres in NOD spleen has been documented [138], and germinal centres have even been detected within the lymphoid mass infiltrating the pancreas itself [139,140]. Although IL-21 is the characteristic cytokine associated with Tfh cells, they are also known to be capable of producing other cytokines, including IFN-g, which could explain the association of this cytokine with T1D [112,141].…”

Regulatory B cells in autoimmune diseases

“…B cells are among the earliest cells to infiltrate the pancreatic islets in NOD mice, which is where they organize with T cells into lymphoid structures within germinal centers that promotes the selection of autoreactive B cells. 49,50 These ectopic lymphoid structures, which consist of a central zone of T cells surrounded by B cells, begin to generate at the early stage of peri-insulitis. 51 Because B cell-deficient NOD mice fail to develop diabetes, targeting B cells may be a potential approach to treating b-cell mediated autoimmune diabetes.…”

B Lymphocyte Depletion by CD20 Monoclonal Antibody Prevents Diabetes in Nonobese Diabetic Mice despite Isotype-Specific Differences in FcγR Effector Functions

“…B cells are among the earliest cells to infiltrate the pancreatic islets of NOD mice (6,7), where they organize along with T cells into lymphoid structures with germinal centers that may promote the selection of autoreactive B cells (8). Due to defects in B cell tolerance, NOD mice exhibit elevated serum IgG levels and produce anti-insulin and pancreas-specific autoantibodies, as well as natural thymocytotoxic autoantibodies (9).…”