Co-infection increases retention of T. muris helminths. The burden of T. muris worms were determined from the caecum and 3 inches of the colon of BALB/c mice infected according to the experimental design as shown in Figure 1A. Worm counts in T. muris-only BALB/c (clear circle) and IL-4KO (triangle) strains and co-infected BALB/c (square) mice infected with a low (A) and high (B) dose of helminth eggs. Data represents combined results of 2 individual experiments of 4–5 animals per group. P values <0.05 were considered statistically significant. (*p ≤ 0.05).