Unstable Foxp3+ regulatory T cells and altered antigen-presenting cells are associated with lipopolysaccharide-induced fetal loss in pregnant IL10 deficient mice

Maternal IL10 deficiency elevates susceptibility to fetal loss induced by the model Toll-like receptor agonist lipopolysaccharide, but the mechanisms are not well elucidated. Here we show that Il10 null mutant (Il10-/-) mice exhibit altered local T cell responses in pregnancy, exhibiting pronounced hyperplasia in para-aortic lymph nodes draining the uterus with >6-fold increased CD4+ and CD8+ T cells compared with wild-type controls. Amongst these CD4+ cells, Foxp3+ Treg cells were substantially enriched, with 11-fold higher numbers at day 9.5 post coitum (pc). Lymph node hypertrophy in Il10-/- mice was associated with more activated phenotypes in dendritic cells and macrophages, with elevated expression of MHCII, scavenger receptor and CD80. Affymetrix microarray revealed an altered transcriptional profile in Treg cells from pregnant Il10-/- mice, with elevated expression of Ctse (cathepsin E), Il1r1, Il12rb2 and Ifng. In vitro, Il10-/- Treg cells showed reduced steady state Foxp3 expression, and polyclonal stimulation caused greater loss of Foxp3 and reduced capacity to suppress IL17 in CD4+Foxp3- T cells. We conclude that despite a substantially expanded Treg cell pool, diminished stability of Treg cells, increased numbers of effector T cells, and altered phenotypes in dendritic cells and macrophages in pregnancy all potentially confer vulnerability to inflammation-induced fetal loss in Il10-/- mice. These findings suggest a pivotal role for IL10 in facilitating robust immune protection of the fetus from inflammatory challenge and suggest IL10 deficiency could contribute to human gestational disorders where altered T cell responses are implicated.

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Prins JR, Zhang B, Schjenken JE, Guerin LR, Barry SC, Robertson SA