Abstract
Objectives In multiple sclerosis (MS), antigen presenting cells including dendritic cells (DCs) present autoantigens to and activate autoreactive lymphocytes. Many current treatments are broadly immunosuppressive. A more targeted and individualised strategy is to re-establish immune tolerance by exposing DCs to tolerogenic stimuli together with cognate autoantigens specific to HLA haplotype. RASGRP2 has been identified as an MS autoantigen in HLA-DRB1*15:01 (DR15)-positive individuals. We aimed to develop tolerogenic DCs as immunotherapy for MS.
Methods CD14+ monocytes isolated from peripheral blood mononuclear cells of people with MS and healthy donors were differentiated to DCs under different conditions and co-cultured with autologous CD4+ T-cells. DC surface molecule expression, myelin phagocytosis and T-cell proliferation were assessed by flow cytometry, and cytokine production by bead-based immunoassay. DNA extracted from blood was used for DR15 genotyping. Antigen presenting cells from different individuals were incubated with a library of synthesised RASGRP2-derived peptides of varying DR15 binding affinities to examine presentation using immunopeptidomic techniques and immune reactivity.
Results DCs treated with dexamethasone developed tolerogenic properties including lower surface MHC-II and co-stimulatory molecule expression, lower pro-inflammatory cytokine production, increased myelin debris phagocytosis and reduced proliferation of co-cultured CD4+ T-cells. We observed HLA-DR15 genotype-dependent differences in co-stimulatory molecule expression and dexamethasone response. RASGRP2 peptides with moderate DR15 binding affinity elicited the greatest immune reactivity in people with MS compared with healthy controls.
Conclusions DCs with tolerogenic properties could be generated from peripheral blood. Priming with relevant autoantigens may stimulate disease-specific immune tolerance, leading to more targeted and personalised MS treatments.
