Suppressive mechanisms by Heligmosomoides polygyrus-induced Tregs in C57BL/6 mice change over time and differ to that of naïve mice.

Disrupting or harnessing immune suppression is leading to new therapeutic avenues in a number of immune-related diseases. Understanding the suppressive functions of regulatory T cells (Tregs) in different environments is therefore key. Parasitic worms are strong inducers of Tregs and previous research has suggested that parasite-induced Tregs are stronger suppressors than naive Tregs. In strains susceptible to the intestinal worm Heligmosomoides polygyrus, like C57BL/6 mice, it has been hypothesized that increased Treg suppression downregulates both Th1 and Th2 responses, leading to chronic infections and high worm burden. Here, we show that the suppressive capacity of Tregs is no different between cells from infected and/or naive animals. In vitro suppression induced by CD4(+)CD25(+)Tregs (Peyers' Patches or the mesenteric lymph nodes), isolated early (day 7, tissue dwelling phase) or late (day 21, luminal phase) during infection was similar to that induced by cells from naive animals. Suppression was CTLA-4 dependent in Tregs from acute but not chronic infection or in Tregs from naive animals. This highlights the versatility of Tregs and the importance of extensive Treg characterization prior to potential in vivo manipulation of this cell type.