Lamina Propria CD4+Lap+ T Cells Show In Vitro Regulatory Activity and are Selectively Increased in Active Ulcerative Colitis

Background: A CD4+CD25- regulatory T cell population expressing the surface TGF-) in its latent form LAP (Latency Associated Peptide) was previously identified and proved to be protective in the adoptive transfer colitis model (J. Immunol. 2003,170:2516). In recent studies we demonstrated that lamina propria (LP) CD4+LAP+ T cells population appears to be relevant to protect mice from TNBS-induced colitis (J. Immunol. 2005,174: 3237). We also showed, for the first time, the presence of LP CD4+LAP+ T cells in patients with IPAA for ulcerative colitis (UC) (IBD 2008, 14: 662). Recently peripheral blood (PB) CD4+LAP+ T cells from healthy subjects have been shown to inhibit the proliferation of PB CD4+LAP− T cells (J. Immunol. 2010,184;4620). More recently induced CD4+LAP+ T cells have been reported to reduce the TNF-( production by LPS treated PBMC(peripheral blood mononuclear cells). (Immunol. 2011, 133; 278). Aim: In the present study we investigated the prevalence and function of LP CD4+LAP+ T cells in inflammatory bowel disease (IBD) patients. Methods: Specimens from patients undergoing colonscopy or bowel resection for IBD and cancer were used as the source of LPMC. UC groups were divided according to endoscopic activity (modified Baron index -New Eng J Med 2005;352: 2499). IL- 17 production, LAP and Foxp3 expression in CD3/CD4 gated cell population was assessed ex-vivo by immunofluorescence. CD4+LAP+CD25- and CD4+LAP- CD25- LP cells were FACS-sorted for functional studies. Results: In initial studies we found that LPMC from Crohn's disease(CD) patients showed a reduced % CD4+LAP+ T cells while LPMC from UC patients showed an increased proportion of CD4+LAP+ T cells when compared to controls. In subsequent studies, we found that the majority of LP CD4+LAP+ from UC patients were Foxp3- and that LP CD4+LAP+ CD25- sorted cells from mild UC specimens or controls were able to inhibit the proliferation of In Vitro (CD3/28 stimulated autologous LP and PB CD4+LAPCD25- cells. The % of CD4+LAP+ cells was significantly higher in LPMC isolated from moderate to severe active UC patients when compared to mild / inactive patients who showed values comparable to controls (C) (10.3%±2 UC vs 3.5%±1.5 C; mean ± SEM, p=0.015). Initial characterization of these cells showed that a variable proportion (0-26%) of LP CD4+ LAP+ gated T cells were IL-17+. The proportion of LP CD4+ LAP+ gated T cells was significantly higher in active UC patients when compared to control patients (19.6%±1 vs 3.4% ± 2.2, respectively, p=.00029). LP CD4+IL-17+cells were also increased in active patients when compared to C. Conclusions: In humans, LP CD4+LAP+ cells show regulatory activity. In IBD, they are selectively increased in active UC patients where a proportion of LP CD4+LAP+ cells show IL- 17 expression.