CD4+FoxP3+ Regulatory T Cells from Gαi2−/− Mice Are Functionally Active In Vitro, but Do Not Prevent Colitis

Abstract

BackgroundMice deficient in the inhibitory G protein subunit Gαi2 spontaneously develop a T helper 1 dominated colitis. We examined whether a defect in CD4+FoxP3+ regulatory T cells (Treg) underpins the pathogenesis of colitis in the Gαi2−/− (Gαi2-deficient) colitis model.Methodology/Principal FindingsUsing flow cytometry, we found that thymus and colonic lamina propria, but not spleen and mesenteric lymph nodes, of colitic Gαi2−/− mice contained increased frequencies of Treg, whereas FoxP3 expression intensity was similar in Gαi2−/− compared to Gαi2+/− or Gαi2+/+ wild type (WT) mice. The frequency of CD4+FoxP3+ T cells expressing CD103 was significantly increased in Gαi2−/− compared to WT mice. Treg in colons from WT mice clustered in the T cell areas of colonic lymphoid patches (CLP), with relatively few Treg in the lamina propria, as demonstrated by immunohistochemistry. In Gαi2−/− mice, CLP were not observed but lamina propria Treg were increased in number and frequency within the CD4+ infiltrate, compared to WT mice. Using an in vitro co-culture system and flow cytometric analysis of cell division we could demonstrate that the in vitro suppressive function of WT and Gαi2−/− CD4+FoxP3+ regulatory T cells (WT-Treg and KO-Treg) was indistinguishable, but that T effector cells (CD4+25− T cells) from Gαi2−/− mice were less readily suppressed than WT effectors (WT-Teff) by Treg from either source. However, neither WT nor Gαi2−/− Treg was able to suppress colitis induced by adoptive transfer of Gαi2−/− effector T cells (KO-Teff) to RAG2−/− recipients. The enhanced inflammatory activity of Gαi2−/− effectors was accompanied by increased expression of an effector/memory T cell phenotype and increased cytokine secretion, especially IL-4, IL-6 and IFN-γ.ConclusionsThere is an increased frequency of Gαi2−/− Treg in the colon, and they demonstrate no endogenous functional defect. However, Gαi2−/− T effector cells are dramatically less susceptible to suppression in vitro, and in vivo, despite increased effective numbers of Treg, they cannot prevent disease.

Microscopic Colitis as a Diagnosis to Consider by Clinicians and Pathologists Together: A Case Series and Review of Literature

“…Increased frequencies of Foxp3+ CD4+ Tregs have also been reported in Crohn's disease and ulcerative colitis [97]. We have demonstrated in a mouse model of colitis that whereas the suppressive function of FoxP3+ Tregs was similar between wild-type mice and mice with colitis, CD4+ effector T cells from colitic mice were much less suppressed by Tregs irrespective of if they were derived from colitic or wild-type mice [98]. Therefore, the problems seemed to be confined to the effector T cells being resistant to Treg-mediated suppression.…”

Loss of Gαi proteins impairs thymocyte development, disrupts T-cell trafficking, and leads to an expanded population of splenic CD4+PD-1+CXCR5+/− T-cells

“…However, treating wild type CD4 T cells with pertussis toxin failed to reproduce these abnormalities. Furthermore, in Gnai2 −/− colitis prone mice, regulatory T cells did not normally inhibit effector memory CD4 T cells 23 . While intriguing these studies are complicated by variations in mouse genetic backgrounds, and that thymic T cells development occurs in a globally Gα i2 deficient animal or a Gnai2 −/− bone marrow reconstituted wild type animal.…”

Diagnosis and management of microscopic colitis: current perspectives

“… 101 We have demonstrated in a mouse model of colitis that whereas the suppressive function of FoxP3 + T regs was similar between wild-type mice and mice with colitis, CD4 + effector T cells from colitic mice were much less suppressed by T regs irrespective of if they were derived from colitic or wild-type mice. 102 Therefore, the problems seemed to be confined to the effector T cells being resistant to T reg -mediated suppression.…”