Lymphatic endothelial cells (LEC) express a variety of peripheral tissue antigens (Ags) and induce deletional tolerance of tyrosinase-specific CD8 T cells. LEC express MHC II molecules, suggesting they may tolerize CD4 T cells. We expressed β-galactosidase (β-gal) selectively in LEC using Lyve-1cre x β-galflox mice to investigate the ability of LEC to tolerize β-gal specific CD4 and CD8 T cells (Bg2 and Bg1, respectively). Using in vitro co-cultures and MHC I-/- bone marrow chimeras, we demonstrated that Bg1 CD8 T cells undergo deletional tolerance after recognizing Ag presented by MHC I molecules on LEC. Peptide-pulsed LEC induce Bg2 CD4 T cell proliferation in vitro, indicating LEC express functional MHC II. However, Bg2 cells proliferate when co-cultured with CD11c cells but not with LEC from β-gal+ mice. When Ag presentation is restricted to LEC in MHC II-/- bone marrow chimeras, Bg2 cells do not proliferate or upregulate CD69, CD25 or CD44. However, Bg2 cells do proliferate when transferred into chimeras with MHC II+ β-galneg bone marrow, demonstrating that hematopoietic cells acquire and present Ag from LEC. Bg2 cells activated in vivo by hematopoietic presentation of LEC-derived Ag do not proliferate in response to subsequent rechallenge, demonstrating that they have become anergic. Thus, LEC show a diminished ability to directly present MHC II Ags, but play an important role in CD4 tolerance by serving as a reservoir of Ag used by hematopoietic cells to induce anergy.
- Copyright © 2013 by The American Association of Immunologists, Inc.