[1] Univ Penn, Sch Vet Med, Dept Pathobiol, Philadelphia, PA 19104 USA
[2] Univ Penn, Penn Genome Frontiers Inst, Dept Biol, Philadelphia, PA 19104 USA
[3] DNAX Discovery Res, Merck Res Labs, Palo Alto, CA 94304 USA
[4] Univ Penn, Dept Med, Philadelphia, PA 19104 USA
[5] NIAID, Mucosal Immunol Unit, Parasit Dis Lab, NIH, Bethesda, MD 20892 USA
[6] Harvard Univ, Beth Israel Deaconess Med Ctr, Sch Med, Transplant Inst, Boston, MA 02215 USA