NK1.1 and AsGm-1 expressing cells play a role in
immunomodulation. Our purpose was to determine the role of NK1.1+ and AsGm-1+ expressing cells in the inflammatory/tolerance paradigm in experimental
colitis. Oral tolerance towards
colitis-extracted
proteins had previously been shown to alleviate experimental
colitis.
Colitis was induced in C57/B6 mice by intracolonic instillation of
trinitrobenzenesulfonic acid (TNBS). Oral tolerance was induced via five oral doses of
proteins extracted from TNBS-
colitis colonic wall. Clinical, macroscopic, and microscopic scores were used for
colitis assessment. To evaluate the putative role of AsGm-1 in tolerance induction, depletion of AsGm-1 expressing cells was performed. To evaluate the mechanism of tolerance induction, liver-associated NKT lymphocytes were harvested 14 days following tolerance induction, and cultured with
concanavalin A (con A) and
colitis-extracted
proteins. T cell subsets were measured by flow cytometry.
Cytokine expression was measured by intracellular staining and
enzyme-linked
immunosorbent assay (ELISA). Orally tolerized mice exhibited significant alleviation of the clinical, macroscopic, and microscopic parameters of
colitis, with increased CD4+ILA+/CD4+IFNgamma+ lymphocyte ratio, increased
IL-4, and decreased IFNgamma and
IL-12 serum levels. In contrast, orally fed mice that were AsGm-1 depleted showed evidence of severe
colitis. These mice exhibited significant decreased CD4 +
IL4+/CD4+IFNgamma+ ratios, and an increase in IFNgamma and
IL-12, with decreased
IL-4 levels. NKT cells harvested from tolerized mice secreted high levels of antiinflammatory
cytokines. In contrast, in nontolerized mice, NKT cells mainly secreted proinflammatory
cytokines. In a tolerized environment, both NK1.1 and AsGm-1 expressing cells are essential for disease alleviation. In contrast, in a nontolerized environment, AsGm-1 expressing cells support an antiinflammatory immune paradigm, while NKT lymphocytes support a proinflammatory shift.