Abstract
Purpose: :
Hydrodynamic injection of an IRBP DNA vaccine can protect mice from EAU by inducing IRBP-specific CD4+CD25+FoxP3+ T regulatory cells (Treg). These Tregs could be expanded into functionally stable lines and transfer protection to EAU-challenged recipient mice. The present study examines the suppressive characteristics and in vivo migration of the vaccination-induced Treg cells.
Methods: :
Treg lines were derived from FoxP3-GFP reporter, CD90 allotype-marked B10.RIII donor mice and stimulated with IRBP peptide on bone marrow dendritic cells and IL-2. To study the suppressive function of the Treg cells, they were co-cultured with 1) naïve IRBP TCR transgenic (Tg) cells; 2) IRBP TCR Tg cells undergoing a 2ndary Ag stimulation in vitro (recently primed), and 3) a stably polarized, long term uveitogenic Th1 cell line. To study the migration of the Tregs during active disease, 10 million cultured Treg cells were infused into uveitic mice that had been immunized with IRBP 10 days earlier. Transferred Tregs retrieved from recipient mice were identified by flow cytometry for FoxP3 and CD90.
Results: :
In functional in vitro suppression studies the Tregs inhibited proliferation and development of IFNγ producing cells from naïve and from recently primed IRBP TCR Tg cells by 3 to 7-fold. However, IFN-γ production by a stably polarized Th1 cell line was not affected. Tregs infused into uveitic mice localized in lymph nodes and spleen as well as in the eye, and could still be detected as late as 9 days after transfer (latest timepoint examined).
Conclusions: :
Vaccination-induced Tregs are effective in controlling naïve as well as recently primed effector T cells, but committed Th1 effectors are not sensitive to suppression. Upon transfer to uveitic hosts, the Tregs localize in vivo to peripheral lymphoid organs and to the target organ, where they might conceivably encounter all three types of effector cells, depending on disease stage. Suppressive function of transferred Treg cells retrieved from uveitic hosts is currently being investigated.
Keywords: autoimmune disease • uveitis-clinical/animal model • proliferation