Characterization of the T Lymphocyte Subsets and Lymphoid Populations Involved in the Induction of Low-Dose Oral Tolerance to Human Thyroglobulin

Using mice deficient in CD8α, TCRδ, CD4, or CD120a, as well as adoptive transfer experiments in wild-type and RAG-1-deficient mice, we characterized the T lymphocyte subsets and lymphoid populations involved in the induction of low-dose oral tolerance to human thyroglobulin (hTg). The oral administration of hTg, but not the intraperitoneal (ip) administration of hTg, generates lymphocytes that can transfer tolerance. Purified CD8α+ lymphocytes successfully transfer tolerance, while the depletion of CD8α or TCRδ lymphocytes prevents the transfer of tolerance. Oral tolerance can be induced in CD4-deficient mice and RAG-1-deficient mice reconstituted with cells from CD120a-deficient mice, but not in CD8α-, TCRδ, or CD120a-deficient mice. These findings indicate that CD8α and TCRδ T lymphocytes are necessary for the oral induction and transfer of tolerance to hTg. Additionally, functional Peyerʹs patches are necessary for the induction of low-dose oral tolerance to hTg.