The effect of abatacept on T-cell activation is not long-lived in vivo.

Abatacept, a co-stimulatory blocker comprising the extracellular portion of human CTLA-4 linked to the Fc region of IgG1, is approved for the treatment of rheumatoid arthritis. By impairing the interaction between CD28 on T cells and CD80/CD86 on APCs, its mechanisms of action include the suppression of follicular T helper cells (preventing the breach of self-tolerance in B cells), inhibition of cell cycle progression holding T cells in a state described as 'induced naïve' and reduction in DC conditioning. However, less is known about how long these inhibitory effects might last, which is a critical question for therapeutic use in patients. Herein, employing a murine model of OVA-induced DTH, we demonstrate that the effect of abatacept is short-lived in vivo and that the inhibitory effects diminish markedly when treatment is ceased.

Revealing stromal and lymphoid sources of Col3a1-expression during inflammation using a novel reporter mouse.

One of the earliest signs of dysregulation of the homeostatic process of fibrosis, associated with pathology in chronic conditions such as rheumatoid arthritis, is the overexpression of collagen type III (COL-3). Critically, there is still relatively little known regarding the identity of the cell types expressing the gene encoding COL-3 (Col3a1). Identifying and characterizing Col3a1-expressing cells during the development of fibrosis could reveal new targets for the diagnosis and treatment of fibrosis-related pathologies. As such, a reporter mouse expressing concomitantly Col3a1 and mKate-2, a fluorescent protein, was generated. Using models of footpad inflammation, we demonstrated its effectiveness as a tool to measure the expression of COL-3 during the repair process and provided an initial characterization of some of the stromal and immune cells responsible for Col3a1 expression.

Phenotypically distinct anti-insulin B cells repopulate pancreatic islets after anti-CD20 treatment in NOD mice.

AIMS/HYPOTHESIS: Autoreactive B cells escape immune tolerance and contribute to the pathogenesis of type 1 diabetes. While global B cell depletion is a successful therapy for autoimmune disease, the fate of autoreactive cells during this treatment in autoimmune diabetes is unknown. We aimed to identify and track anti-insulin B cells in pancreatic islets and understand their repopulation after anti-CD20 treatment. METHODS: We generated a double transgenic system, the VH125.hCD20/NOD mouse. The VH125 transgenic mouse, expressing an increased frequency of anti-insulin B cells, was crossed with a human CD20 (hCD20) transgenic mouse, to facilitate B cell depletion using anti-CD20. B cells were analysed using multiparameter and ImageStream flow cytometry. RESULTS: We demonstrated that anti-insulin B cells were recruited to the pancreas during disease progression in VH125.hCD20/NOD mice. We identified two distinct populations of anti-insulin B cells in pancreatic islets, based on CD19 expression, with both populations enriched in the CD138int fraction. Anti-insulin B cells were not identified in the plasma-cell CD138hi fraction, which also expressed the transcription factor Blimp-1. After anti-CD20 treatment, anti-insulin B cells repopulated the pancreatic islets earlier than non-specific B cells. Importantly, we observed that a CD138intinsulin+CD19- population was particularly enriched after B cell depletion, possibly contributing to the persistence of disease still observed in some mice after anti-CD20 treatment. CONCLUSIONS/INTERPRETATION: Our observations may indicate why the loss of C-peptide is only temporarily delayed following anti-CD20 treatment in human type 1 diabetes.

B cell depletion reduces T cell activation in pancreatic islets in a murine autoimmune diabetes model.

AIMS/HYPOTHESIS: Type 1 diabetes is a T cell-mediated autoimmune disease characterised by the destruction of beta cells in the islets of Langerhans, resulting in deficient insulin production. B cell depletion therapy has proved successful in preventing diabetes and restoring euglycaemia in animal models of diabetes, as well as in preserving beta cell function in clinical trials in the short term. We aimed to report a full characterisation of B cell kinetics post B cell depletion, with a focus on pancreatic islets. METHODS: Transgenic NOD mice with a human CD20 transgene expressed on B cells were injected with an anti-CD20 depleting antibody. B cells were analysed using multivariable flow cytometry. RESULTS: There was a 10 week delay in the onset of diabetes when comparing control and experimental groups, although the final difference in the diabetes incidence, following prolonged observation, was not statistically significant (p = 0.07). The co-stimulatory molecules CD80 and CD86 were reduced on stimulation of B cells during B cell depletion and repopulation. IL-10-producing regulatory B cells were not induced in repopulated B cells in the periphery, post anti-CD20 depletion. However, the early depletion of B cells had a marked effect on T cells in the local islet infiltrate. We demonstrated a lack of T cell activation, specifically with reduced CD44 expression and effector function, including IFN-γ production from both CD4+ and CD8+ T cells. These CD8+ T cells remained altered in the pancreatic islets long after B cell depletion and repopulation. CONCLUSIONS/INTERPRETATION: Our findings suggest that B cell depletion can have an impact on T cell regulation, inducing a durable effect that is present long after repopulation. We suggest that this local effect of reducing autoimmune T cell activity contributes to delay in the onset of autoimmune diabetes.