Abstract
Purpose::
We have evidence that pre-treatment with differentially-LPS-activated bone marrow-derived dendritic cells (BMDC), either IL10- (eDC) or IL12- (lDC) secreting, can significantly suppress IRBP-induced Experimental Autoimmune Uveoretinitis (EAU) in C57Bl/6 mice. EAU suppression by eDC appears to be mediated by CD4+CD25+Foxp3+ regulatory T cells (Tregs). The aim of this study is to investigate how Tregs are induced by eDC to suppress EAU.
Methods::
Differentially-activated BMDC or Tregs were adoptively transferred subcutaneously (at the nape) 24 hours prior to the induction of EAU (at the inguinal). Tregs were isolated by positive depletion of non-CD4+ cells then double positive selection of CD25high cells. Cytokine bead assay (CBA) and flow cytometry were used to study the DC phenotype and cytokine profile. The draining cervical lymph nodes were harvested three days post-DC transfer, and the Tregs studied by flow cytometry.
Results::
We confirm here that the adoptive transfer of eDC significantly expands Tregs at the draining lymph node (dLN) in vivo and the adoptive transfer of these Tregs inhibits EAU. We now show thateDC-induced Tregs and naïve endogenous Tregs both inhibit EAU in a dose dependent manner, with the latter in an antigen-independent manner also. However, eDC from MHCII-/- mice fail to suppress EAU, suggesting a requirement for antigen in this process. Suprisingly, eDC from MHCII-/- mice also induce the expansion of the Treg population at dLN in vivo. However, at distal lymph nodes, such expansion of Tregs is only observed in WTeDC-treated, not MHCII-/- eDC-treated mice.
Conclusions::
These data suggest that endogenous naïve Tregs have an inbuilt capacity to inhibit autoimmunity non-specifically, but induced Tregs require antigen presentation for this function.
Keywords: uveitis-clinical/animal model • immunomodulation/immunoregulation • autoimmune disease