Antigen-induced tolerance by intrathymic modulation of self-recognizing inhibitory receptors.

CD1d-restricted invariant natural killer T cell (iNKT cells) have a limited T cell receptor (TCR) repertoire and share characteristics common to T cells and natural killer cells. While intrathymic selection facilitates the production of T cells carrying self major histocompatibility complex-restricted TCRs, natural killer cells carry an appropriate repertoire of self major histocompatibility complex-recognizing receptors to avoid self-reactivity. Here we show that chronic exposure to specific glycolipid antigen resulted in iNKT cell disappearance and thymus-dependent repopulation of iNKT cells with increased expression of inhibitory Ly-49 molecules that resulted in impaired responsiveness. Thymic selection of peripheral Ly-49-expressing iNKT cell repertoire inhibited cytokine production and other functions in vivo. These observations emphasize the acquisition of self-recognizing inhibitory receptors on NKT cells as a previously unknown mechanism of thymic tolerance after chronic antigen exposure.