Intraepithelial lymphocytes traffic to the intestine and enhance resistance to Toxoplasma gondii oral infection

Toxoplasma gondii Ag-primed intraepithelial lymphocytes (IEL) from the mous e intestine have been shown to be protective against an lethal parasite cha llenge when adoptively transferred into recipient mice. In the present stud y, we observed that Ag-primed IEL traffic to the intestine of naive mice fo llowing i.v. administration. Primed and CD8 beta(+) IEL were the most effic ient cells at homing to the host organ. In congenic mice, IEL migrated from intestine within several hours posttransfer, On Ag reexposure, the primed IEL return to the intestine where they enhance resistance as determined by reduction in the number of brain cysts. Treatment of recipient mice with an ti-alpha(4) and anti-alpha(E) Abs partially inhibited IEL intestinal homing . The Ab treatment dramatically impaired resistance to a subsequent oral in fection. These finding indicate that lymphocyte homing is an important para meter in establishing long term immunity to recurrent infection with this p arasite.