Low-level regulatory T-cell activity is essential for functional type-2 effector immunity to expel gastrointestinal helminths

Helminth infection is frequently associated with the expansion of regulatory T cells (Tregs) and suppression of immune responses to bystander antigens. We show that infection of mice with the chronic gastrointestinal helminth Heligmosomoides polygyrus drives rapid polyclonal expansion of Foxp3(+)Helios(+)CD4(+) thymic (t)Tregs in the lamina propria and mesenteric lymph nodes while Foxp3(+)Helios(-)CD4(+) peripheral (p)Treg expand more slowly. Notably, in partially resistant BALB/c mice parasite survival positively correlates with Foxp3(+)Helios(+)CD4(+) tTreg numbers. Boosting of Foxp3(+)Helios(+)CD4(+) tTreg populations by administration of recombinant interleukin-2 (rIL-2):anti-IL-2 (IL-2C) complex increased worm persistence by diminishing type-2 responsiveness in vivo, including suppression of alternatively activated macrophage and granulomatous responses at the sites of infection. IL-2C also increased innate lymphoid cell (ILC) numbers, indicating that Treg functions dominate over ILC effects in this setting. Surprisingly, complete removal of Tregs in transgenic Foxp3-DTR mice also resulted in increased worm burdens, with "immunological chaos" evident in high levels of the pro-inflammatory cytokines IL-6 and interferon-γ. In contrast, worm clearance could be induced by anti-CD25 antibody-mediated partial depletion of early Treg, alongside increased T helper type 2 responses and without incurring pathology. These findings highlight the overarching importance of the early Treg response to infection and the non-linear association between inflammation and the prevailing Treg frequency

Properties and Immune Function of Cardiac Fibroblasts.

This chapter will discuss the role of cardiac fibroblasts as a target of various immunological inputs as well as an immunomodulatory hub of the heart through interaction with immune cell types and chemokine or cytokine signaling. While the purpose of this chapter is to explore the immunomodulatory properties of cardiac fibroblasts, it is important to note that cardiac fibroblasts are not a homogeneous cell type, but have a unique embryological origin and molecular identity. Specific properties of cardiac fibroblasts may influence the way they interact with the heart microenvironment to promote healthy homeostatic function or respond to pathological insults. Therefore, we will briefly discuss these aspects of cardiac fibroblast biology and then focus on their immunomodulatory role in the heart. Adv Exp Med Biol 2017; 1003:35-70