T-helper cell phenotypes are repeatable, positively correlated, and associated with helminth infection in wild Soay sheep.

Background: T-helper (Th) cells co-ordinate immune responses to ensure that infections with diverse parasites are controlled effectively. Helminth parasites such as gastrointestinal nematodes (GIN) are generally associated with T-helper type 2 (Th2) responses, while intracellular parasites are associated with Th1 responses. Although laboratory models have reported that Th1 and Th2 can be antagonistic, this has been challenged by studies of natural infections.