CXCR5 and helminthiasis: T follicular helper (Tfh) cells are IL-4gfp+ and express PD-1 during helminth infection [39], [40], [41], and as expected the increases in tLN IL-4gfp+ T cells observed during L. sigmodontis infection represented an expansion of both IL-4gfp+CXCR5− Th2 cells and IL-4gfphighCXCR5+ Tfh cells (Figure 3D).