Thymus-Derived Regulatory T Cells Exhibit Foxp3 Epigenetic Modification and Phenotype Attenuation after Mating in Mice

Abstract

Regulatory T cells (Tregs) are essential for maternal tolerance in allogeneic pregnancy. In preeclampsia, Tregs are fewer and display aberrant phenotypes, particularly in the thymic Treg (tTreg) compartment, potentially because of insufficient priming to male partner alloantigens before conception. To investigate how tTregs as well as peripheral Tregs (pTregs) respond to male partner seminal fluid, Foxp3 + CD4 + Tregs were examined in the uterus and uterus-draining lymph nodes in virgin estrus mice and 3.5 d postcoitum. Mating elicited 5-fold increases in uterine Tregs accompanied by extensive Treg proliferation in the uterusdraining lymph nodes, comprising 70% neuropilin 1 + tTregs and 30% neuropilin 1 2 pTregs. Proliferation marker Ki67 and suppressive competence markers Foxp3 and CTLA4 were induced after mating in both subsets, and Ki67, CTLA4, CD25, and GITR were higher in tTregs than in pTregs. Analysis by t-stochastic neighbor embedding confirmed phenotypically distinct tTreg and pTreg clusters, with the proportion of tTregs but not pTregs among CD4 + T cells expanding in response to seminal fluid. Bisulphite sequencing revealed increased demethylation of the Treg-specific demethylation region in the Foxp3 locus in tTregs but not pTregs after mating. These data show that tTregs and pTregs with distinct phenotypes both respond to seminal fluid priming, but the Foxp3 epigenetic signature is uniquely increased in tTregs. We conclude that reproductive tract tTregs as well as pTregs are sensitive to local regulation by seminal fluid, providing a candidate mechanism warranting evaluation for the potential to influence preeclampsia susceptibility in women.

Exploring the Origin and Antigenic Specificity of Maternal Regulatory T Cells in Pregnancy

“…Despite this decrease, however, these authors found increased proliferative activity of RTE-tT Regs with superior suppressive activity compared to more mature T Reg cells. Consistent with this idea, in mice, tT Reg cells as defined by Nrp1 expression and demethylated status of the CNS2, proliferate in the uterusdraining para-aortic LNs as early as GD3.5 (59). The presence of organ-specific antigens can trigger local expansion of organspecific T Reg cells in draining LNs with considerable inter-organ differences in TCR usage by T Reg (16).…”

“…Nrp1 functions to increase sensitivity of T Reg to antigen and permit prolonged interaction with immature dendritic cells ( 57 ). Further, its expression is associated with prolonged survival of allogeneic grafts in mice ( 58 ) as well as demethylation at the CNS2 region of the Foxp3 locus ( 59 ), which is characteristic of tT Regs . On the other hand, 90% of CD4+CD8+ DP cells in the thymus are Nrp1+ ( 60 ) and can also be induced in conventional CD4+ T cells in vitro ( 58 ).…”

“…The presence of organ-specific antigens can trigger local expansion of organ-specific T Reg cells in draining LNs with considerable inter-organ differences in TCR usage by T Reg ( 16 ). As such, tT Reg in uterus-draining LNs are likely responding specifically to fetal/paternal antigens in the para-aortic LNs by proliferation ( 59 ). The notion of early recruitment of tT Reg cells to the decidua was also suggested by Teles et al who demonstrated increased Foxp3+ Helios+ T Reg cells in the thymus, uterus-draining LNs, and uterus by day 2 of murine pregnancy ( 76 ).…”

Prednisolone in early pregnancy inhibits regulatory T cell generation and alters fetal and placental development in mice

“…1F). Thymic Treg (tTreg) cells and peripheral Treg (pTreg) cells, distinguished on the basis of NRP1 expression (Yadav, et al, 2012), both contribute to the Treg increase in early pregnancy (Moldenhauer, et al, 2019). Both tTreg and pTreg cells in the PALN failed to increase after prednisolone treatment (Fig.…”

Endocrine Disruptor Compounds—A Cause of Impaired Immune Tolerance Driving Inflammatory Disorders of Pregnancy?

“…Implantation only occurs if immune cells in the uterine endometrium exhibit a favourable, permissive response. In particular, expansion and recruitment of specialized immune cells known as regulatory T cells (Treg cells) must occur (95)(96)(97)(98). Treg cells interact with dendritic cells and macrophages to promote decidualisation of uterine stromal cells, suppress inflammation, and inhibit effector immunity towards fetal antigens.…”