Bacterial CD1d-restricted glycolipids induce IL-10 production by human regulatory T cells upon cross-talk with invariant NKT cells.

Invariant NKT (iNKT) cells and CD4(+)CD25(+)FOXP3(+) regulatory T cells (Tregs) are important immune regulatory T cells with Ag reactivity to glycolipids and peptides, respectively. However, the functional interplay between these cells in humans is poorly understood. We show that Tregs suppress iNKT cell proliferation induced by CD1d-restricted glycolipids, including bacterial-derived diacylglycerols, as well as by innate-like activation. Inhibition was related to the potency of iNKT agonists, making diacylglycerol iNKT responses very prone to suppression. Cytokine production by iNKT cells was differentially modulated by Tregs because IL-4 production was reduced more profoundly compared with IFN-γ. A compelling observation was the significant production of IL-10 by Tregs after cell contact with iNKT cells, in particular in the presence of bacterial diacylglycerols. These iNKT-primed Tregs showed increased FOXP3 expression and superior suppressive function. Suppression of iNKT cell responses, but not conventional T cell responses, was IL-10 dependent, suggesting that there is a clear difference in mechanism between the Treg-mediated inhibition of these cell types. Our data highlight a physiologically relevant interaction between human iNKT and Tregs upon pathogen-derived glycolipid recognition that has a significant impact on the design of iNKT cell-based therapeutics.

Preclinical safety evaluation of recombinant human interleukin-10.

Escherichia coli-derived recombinant human interleukin-10 (rhuIL-10) has been evaluated in an extensive series of in vivo and in vitro nonclinical safety studies, including genetic toxicology, single- and repeat-dose systemic toxicity and toxicokinetics, reproductive toxicity, and specialized irritation studies. The primary test species in the toxicology studies were the mouse and monkey based on rhuIL-10 activity in receptor binding and ex vivo cytokine assays. Supported by a detailed preclinical program of therapeutic and prophylactic animal models in autoimmune diseases, the initial clinical development program has focused on investigating the therapeutic potential of rhuIL-10 (Tenovil) in Crohn's disease and rheumatoid arthritis. The results of the subcutaneous toxicity studies, up to 3 months dosing duration in mice and 6 months dosing duration in monkeys, support the development of rhuIL-10 for present and future clinical indications by the subcutaneous route of administration.