Similar Mechanisms Induce CD8+ T Regulatory (Tr) Cells in ACAID and Low Dose Oral Tolerance

Abstract

Abstract: : Purpose: ACAID (anterior chamber associated immune deviation) is a term used to describe immune tolerance associated with the inoculation of antigen into the anterior chamber. Oral tolerance (OT) describes tolerance to orally administered antigens. It is known that efferent CD8+ Tr cells are generated in both ACAID and OT. The goal of this study was to investigate whether OT and ACAID use the same mechanisms during the generation of efferent CD8+ Tr cell. Methods: Endotoxin free ovalbumin (OVA) was administered orally by gavage to wild-type (WT) or knock-out (KO) mice. Tolerance to antigen was measured in a delayed type hypersensitivity assay (DTH) CD1d KO and Jα18 KO mice (with or without CD4+ NKT cell reconstitution) or in a local adoptive transfer DTH assay (LAT-DTH) in MHC Class II KO mice. Flow cytometry was used to confirm enrichment of certain cell subpopulations. Results: Following OT induction T cells from both spleens or mesenteric lymph nodes (mln) of WT mice suppressed the adoptively transferred DTH response. Treatment of the cells with anti-CD8 mab removed this activity. OT could not be induced in mice lacking NKT cells (CD1d KO, Jα18 KO mice). CD8+ T r cells were produced by OT induction in NKT cell reconstituted Jα18 KO mice but not when the NKT cells were depleted of CD4+ cells. Antigen gavage of MHC class II KO resulted in the generation of Tr cells that suppressed DTH in the LAT assay. Conclusions: OT, like ACAID, is dependent on CD1d, indicating a requirement for both NKT cells and the CD1d molecule in the suppression of DTH. The generation of efferent Tr cells in Jα18KO mice (lack the invariant TCR-NKT, (iNKT cell)) that are reconstituted with CD4+ NKT cells and the presence of Tr cells in Class II KO mice indicate that both tolerance models require CD4+ iNKT cells but not conventional CD4+ T for the generation of efferent CD8+ T r cells. Mechanisms of efferent CD8+ Tr induction used by the immune privileged eye might be shared by other non-immune privileged organs and tissues.

Keywords: ACAID • immune tolerance/privilege • immunomodulation/immunoregulation