IL-10 is necessary for the induction of low dose tolerance

Abstract

Oral Tolerance (OT) is defined as the systemic unresponsiveness to an antigen administered by the oral route. Feeding high doses of antigen is believed to lead to deletion or anergy of Ag-specific T-cells, whereas low doses of antigen leads to the generation of regulatory cells producing cytokines such as IL-4, IL-IO and TGF-beta. In the present study we have investigated the role of IL-IO in the induction of high and low dose tolerance in intact mice as well as in murine small bowel loops with or without Peyers Patches (PP). Tolerance was induced by admtinstration of OVA-peptide 323-339 (OVA-pep) by gastric intubation or into the loops for 5 days, followed by immuni,ation with OVA-peptide in Complete Freunds Adjuvant and subsequent restimulation of spleen and lymph node cells in vitro. Low dose tolerance could not be induced in the absence of IL-10, as feeding a low dose of OVA-pxp (0.5 rag) to 1L-10 KO mice, did not result in a sigmflcant reduction of T-cell proliferation or IFN-gamma production compared to nonfed mice. In contrast, feeding the same low dose to wild type C57B1/6 mice resulted in both reduced T-cell proliferation and lFN-gamma production. We then investigated whether IL-10 was necessary for the induction of either low or high dose tolerance in small bowel loops with and without PP. Administration of a low dose of OVA-pep (0.01 mg) into the loops of IL-10 KO mice did not result in the induction of oral tolerance, regardless of whether the loops contained PP or not. However, giving a high dose of OVA-pep (0.5 mg)~to the loops of IL-10 KO mice did induce oral tolerance characterized by reduced T-cell proliferation as well as reduced production of IFN-gamma and IL-2, compared to nonfed mice Again, no differences were observed between loops with and without PP, indicating that high dose tolerance is independent of [L-IO both in the presence and absence of PP. Taken together our results show that IL-10 is necessary for the generation of low dose tolerance, both in the presence and absence of PP, whereas high dose tolerance can be induced independently of IL-IO.