CD4 and helminthiasis: While the number of CD25+ FoxP3+ Treg cells rapidly increased in other models of helminth infection (41, 57, 58), there was no significant increase in the number of FoxP3+ Treg cells as a proportion of CD4+ cells in 4× compared to 1× mice, nor were there differences in the expression levels of CD103 and CTLA-4 markers on FoxP3+ Treg cells or in the abundances of thymic Helios+ Nrp1+ CD4+ cells discrete from peripheral Treg cells.