Effects of depletion of CD4+FoxP3+ Treg on development of spontaneous autoimmune thyroiditis (SAT) in WT and B cell deficient (B-/-) NOD.H-2h4 mice (123.10)

Abstract

Abstract NOD.H-2h4 mice given NaI in their water develop SAT with chronic inflammation of the thyroid by T and B cells. B-/- mice are resistant to SAT, but develop SAT after transient depletion of Treg by anti-CD25. However, NOD.H-2h4 mice have significant numbers of CD4+FoxP3+ Treg that are CD25-. Generation of mice expressing the human diphtheria toxin receptor (DTR) under control of the FoxP3 promoter allows for selective depletion of Foxp3+ cells by diphtheria toxin (DT). Anti-CD25 depletion of Treg lasts 3-4 weeks, whereas most Treg return 4-5 days after DT treatment. In WT and B-/- FoxP3-DTR NOD.H-2h4 mice, injection of DT eliminates essentially all Treg in blood and spleen within 2 days. As with anti-CD25 depletion, DT treatment allows for SAT development in B-/- mice even though Treg are depleted for only a few days, and SAT in DT-treated WT mice is slightly increased. We established a transfer model in which splenocytes from CD28-/-B-/- mice (effector cells) were cultured with or without sorted Treg from FoxP3-DTR WT or B-/- mice. After transfer to TCRα-/- mice, recipients of Treg from B-/- mice developed significantly less severe SAT than did mice receiving Treg from WT mice. As there is no source of new FoxP3-DTR Treg, DT treatment 2 days after transfer to recipient mice resulted in permanent depletion of Treg. This abrogated the suppression, suggesting that suppression of SAT requires continued inhibition of effectors by Treg during disease development.