High resistance to intestinal nematode infection is associated with a strong bias for TFH cell responses, rapid IgG1 class switch and limited Th2 effector cell expansion

Abstract

Abstract Gastrointestinal nematode infections are highly prevalent in nature, lead to considerable morbidity in infected humans and cause high economical loss in animal husbandry. While it is clear that type 2 responses orchestrated by CD4+GATA-3+ Th2 cells are pivotal for the control of GI nematodes, the basis for differential susceptibility of distinct host genetic backgrounds is less well understood. The high resistance of ‘rapid responder’ SJL mice to infections with the small intestinal nematode H. polygyrus is evident in low parasite egg production and the termination of infection within a few weeks. Comparing the SJL line to slow responder C57BL/6 mice, we found that SJL mice generated relatively few Th2 effector cells, many follicular T helper cells and strong antibody responses in spleen and gut draining lymph nodes. These Th2 effector cells of SJL mice expressed high levels of the gut/mucosal homing markers CCR9/a4b7, resulting in the rapid accumulation of Th2 cells in the infected small intestine. Surprisingly, resistance was further associated with exceptionally high proportions of Treg in the spleen of SJL mice at steady state and the vigorous expansion of Treg in mLN after infection. This coincided with a bias for follicular T helper cells expansion in both mLN and spleen and, consequently, more extensive IgG1 class switching by GL7+ germinal center B cells in both organs. Infection-derived B cells transfer provides protection in SJL mice, not in B6 mice. In conclusion, resistance versus susceptibility to primary H. polygyrus infection appears to be less dependent on the overall magnitude of Th2 responses, but rather seems to depend on rapid Th2 effector homing, follicular T helper cells and the rapid instruction of antibody responses.