title: CD4+FoxP3+ regulatory T cells from Gαi2-/- mice are functionally active in vitro, but do not prevent colitis.
abstract: BACKGROUND
  Mice 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.
  
  
  RESULTS
  Using 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.
  
  
  CONCLUSIONS
  There 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.
authors.affiliation: Department of Microbiology & Immunology, Institute of Biomedicine, Mucosal Immunology and Vaccine Center, University of Gothenburg, Gothenburg, Sweden. yu.yuan.gotlind@microbio.gu.se
authors.forename: Yu-Yuan C
authors.initials: YY
authors.lastname: Götlind
authors.forename: Sukanya
authors.initials: S
authors.lastname: Raghavan
authors.forename: Paul W
authors.initials: PW
authors.lastname: Bland
authors.forename: Elisabeth Hultgren
authors.initials: EH
authors.lastname: Hörnquist
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism*; D002455:Cell Division; D018920:Coculture Techniques; D003092:Colitis / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005434:Flow Cytometry / Q000379:methods; D051858:Forkhead Transcription Factors / Q000096:biosynthesis*; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000235:genetics; D005786:Gene Expression Regulation; D018960:Hyaluronan Receptors / Q000096:biosynthesis; D007150:Immunohistochemistry / Q000379:methods; D007413:Intestinal Mucosa / Q000473:pathology; D019041:L-Selectin / Q000096:biosynthesis; D008297:Male; D051379:Mice; D013154:Spleen / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D050378:T-Lymphocytes, Regulatory / Q000378:metabolism*
chemical_list: D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D018960:Hyaluronan Receptors; D019041:L-Selectin; D051960:GTP-Binding Protein alpha Subunit, Gi2; C498016:Gnai2 protein, mouse