Ly49 C/I-dependent NKT cell-derived IL-10 is required for corneal graft survival and peripheral tolerance

C. M. Watte^*, T. Nakamura^*^,1, C. H. Lau^*, J. R. Ortaldo and J. Stein-Streilein^*^,2

^* Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA; and
Laboratory of Experimental Immunology, National Cancer Institute-Center for Cancer Research, Frederick, Maryland, USA

² Correspondence: Schepens Eye Research Institute, Department of Ophthalmology, Harvard Medical School, 20 Staniford Street, Boston, MA 02114, USA. E-mail: joan.stein{at}schepens.harvard.edu

Similar to their activity on NK cells, Ly49 molecules play apivotal role in influencing how NKT cells respond. It is knownthat Ly49 C/I is an inhibitory receptor capable of down-modulatingproliferation, IFN- ${gamma}$ response, and cytotoxic activity in cellsthat express it. In a model of peripheral tolerance inducedvia the eye, we observed that Ly49 C/I-positive, invariant NKTcells were required. To test if the NK inhibitory receptor functionallycontributed to tolerance development, we used blocking antibody,in vivo and in vitro, to interfere with the development of antigen-specificsuppression. A result of blocking ligation of Ly49 C/I inhibitoryreceptor prevented NKT cell production of IL-10 and the subsequentdevelopment of tolerance. Ly49 C/I-blocking antibodies alsoprevented corneal graft survival, a phenomenon dependent oneye-induced tolerance. Furthermore, in the presence of TCR stimulation,cross-linking of Ly49 C/I on CD4⁺ NKT cells stimulated an increasein IL-10 mRNA and a decrease in IFN- ${gamma}$ . The concept of Ly49 inhibitoryreceptors regulating immune reactivity to self by regulatingimmune activity of individual cells is thus expanded to includea role for the inhibitory receptors in the more global processof peripheral tolerance to foreign antigens.

Key Words: NK inhibitory receptors • cytokines • immunosuppression