Studies using the gastrointestinal nematode Trichuris muris typically focus on the E (Edinburgh) isolate. However, two other isolates exist: J (Japan) and S (Sobreda). Earlier experiments showed that following infection with the S isolate of T. muris the C57BL/6 mouse was susceptible and the worms survived, whereas the E and J isolates were expelled. The reason for the prolonged survival of the S isolate is unclear. The purpose of this study was to explore the immunological basis of S isolate survival. Overall, these data suggest that the S isolated has evolved immunomodulatory mechanisms to prolong its survival within the C57BL/6 host.