To test whether Bm-TPI directly stimulates the expansion of Th1 cells, transgenic DO11.10 ovalbumin-specific T cells were co-cultured with ovalbumin peptide and TPI, or co-transferred to naïve mice together with ovalbumin antigen and TPI i.p. However, cytokine responses in TPI recipients were unaltered both in vitro and in vivo (Fig. S3) arguing that the effects of TPI on the effector T cell compartment occur in the setting of an active parasite infection. Here, TPI1 is linked to parasitic infectious disease.