Program in Cell, Molecular, and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, 02111, USA. Program in Cell, Molecular, and Developmental Biology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, 02111, USA. Li.Zeng@tufts.edu. Program of Pharmacology and Experimental Therapeutics, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, 02111, USA. Li.Zeng@tufts.edu. Program of Immunology, Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, MA, 02111, USA. Li.Zeng@tufts.edu. Department of Immunology, Tufts University School of Medicine, Boston, MA, 02111, USA. Li.Zeng@tufts.edu. Department of Orthopaedics, Tufts Medical Center, Boston, MA, 02111, USA. Li.Zeng@tufts.edu.