We have identified that autoimmune BXD2 mice exhibit unique features, including spontaneous formation of germinal centers, increased expression of activation-induced cytidine deaminase (AID), increased production of pathogenic autoantibodies that are polyreactive, significantly increased percentage of IL-17high CD4 TH cells (TH-17) and IL-17Rhigh B cells, and significantly increased numbers of type I interferon producing plasmacytoid dendritic cells in the spleens of these mice. We are currently studying the inter-connection of high IL-17, high type I IFN and the development of autoreactive B cells related to B-cell tolerance loss at the transitional stage and the germinal center stage in BXD2 mice.
We currently study the close interaction between spleen marginal zone (MZ) B cells and MZ macrophages, and the implication of disrupting this close interaction in disease relapse following B-cell depletion therapy (BCDT) in systemic lupus erythematosus (SLE). In healthy individuals, the MZ B cells provide essential signals to maintain MZM survival and tolerogenic signaling to apoptotic debris derived autoantigens (AC-Ags) in the spleen MZ barrier. In SLE, a deficiency of tolerogenic MZMs occurs which disrupts the barrier and promotes an immunogenic environment including accumulation of uncleared AC-Ags and production of type I IFNs. Based on these results, we propose that BCDT in lupus, through depletion of the MZ B cells leads to a secondary depletion of the MZMs which may enable immunogenic responses to ACs in certain SLE patients. During deep B-cell depletion, when there are minimal B cells, this effect is not apparent. However, as B-cell repopulation occurs, the B cells are immediately subject to the immunogenic MZ microenvironment resulting in formation of autoreactive B cells and disease flares. We are currently developing strategies to overcome the loss of tolerogenic MZM barrier following BCDT with an ultimate goal to re-set B-cell tolerogenic state to achieve long-term remission. This work is currently supported by the Lupus Research Institute. http://lupusresearchinstitute.org/lupus-research/grant-recipients/hsu/hui-chen