Alternatively activated (M2) macrophages use fatty acid oxidation for their metabolic needs. Pearce and colleagues show that triacylglycerols metabolized by lysosomal acid lipase are required for the M2 activation of and function of macrophages. Alternative (M2) activation of macrophages driven via the α-chain of the receptor for interleukin 4 (IL-4Rα) is important for immunity to parasites, wound healing, the prevention of atherosclerosis and metabolic homeostasis. M2 polarization is dependent on fatty acid oxidation (FAO), but the source of the fatty acids that support this metabolic program has not been clear. We found that the uptake of triacylglycerol substrates via the scavenger receptor CD36 and their subsequent lipolysis by lysosomal acid lipase (LAL) was important for the engagement of elevated oxidative phosphorylation, enhanced spare respiratory capacity (SRC), prolonged survival and expression of genes that together define M2 activation. Inhibition of lipolysis suppressed M2 activation during infection with a parasitic helminth and blocked protective responses to this pathogen. Our findings delineate a critical role for cell-intrinsic lysosomal lipolysis in M2 activation.

Background: Crohn’s disease is common in highly industrialised Western countries where helminths are rare and uncommon in less developed areas of the world where most people carry worms. Helminths diminish immune responsiveness in naturally colonised humans and reduce inflammation in experimental colitis. Thus exposure to helminths may help prevent or even ameliorate Crohn’s disease. Aims: The aim of the study was to determine the safety and possible efficacy of the intestinal helminth Trichuris suis in the treatment of patients with active Crohn’s disease. Patients: Twenty nine patients with active Crohn’s disease, defined by a Crohn’s disease activity index (CDAI) ⩾220 were enrolled in this open label study. Methods: All patients ingested 2500 live T suis ova every three weeks for 24 weeks, and disease activity was monitored by CDAI. Remission was defined as a decrease in CDAI to less than 150 while a response was defined as a decrease in CDAI of greater than 100. Results: At week 24, 23 patients (79.3%) responded (decrease in CDAI >100 points or CDAI <150) and 21/29 (72.4%) remitted (CDAI <150). Mean CDAI of responders decreased 177.1 points below baseline. Analysis at week 12 yielded similar results. There were no adverse events. Conclusions: This new therapy may offer a unique, safe, and efficacious alternative for Crohn’s disease management. These findings also support the premise that natural exposure to helminths such as T suis affords protection from immunological diseases like Crohn’s disease.

Background & Aims: Ulcerative colitis is most common in Western industrialized countries. Inflammatory bowel disease is uncommon in developing countries where helminths are frequent. People with helminths have an altered immunological response to antigens. In animal models, helminths prevent or improve colitis by the induction of regulatory T cells and modulatory cytokines. This study determined the efficacy and safety of the helminth Trichuris suis in therapy of ulcerative colitis. Methods: This was a randomized, double blind, placebo-controlled trial conducted at the University of Iowa and select private practices. Trichuris suis ova were obtained from the US Department of Agriculture. The trial included 54 patients with active colitis, defined by an Ulcerative Colitis Disease Activity Index of ≥4. Patients were recruited from physician participants and were randomly assigned to receive placebo or ova treatment. Patients received 2500 Trichuris suis ova or placebo orally at 2-week intervals for 12 weeks. Results: The primary efficacy variable was improvement of the Disease Activity Index to ≥4. After 12 weeks of therapy, improvement according to the intent-to-treat principle occurred in 13 of 30 patients (43.3%) with ova treatment compared with 4 of 24 patients (16.7%) given placebo (P = .04). Improvement was also found with the Simple Index that was significant by week 6. The difference in the proportion of patients who achieved an Ulcerative Colitis Disease Activity Index of 0–1 was not significant. Treatment induced no side effects. Conclusions: Ova therapy seems safe and effective in patients with active colitis.

Type 2 innate lymphoid cells (ILC2 cells) contribute to early immune responses directed against helminths and fungi. Paul and colleagues identify distinct inflammatory IL-25-responsive and natural IL-33-responsive ILC2 cells in lung tissues. Innate lymphoid cells (ILCs) are lymphocyte-like cells that lack T cell or B cell antigen receptors and mediate protective and repair functions through cytokine secretion. Among these, type 2 ILCs (ILC2 cells) are able to produce type 2 cytokines. We report the existence of an inflammatory ILC2 (iILC2) population responsive to interleukin 25 (IL-25) that complemented IL-33-responsive natural ILC2 (nILC2) cells. iILC2 cells developed into nILC2-like cells in vitro and in vivo and contributed to the expulsion of Nippostrongylus brasiliensis. They also acquired IL-17-producing ability and provided partial protection against Candida albicans. We propose that iILC2 cells are transient progenitors of ILCs mobilized by inflammation and infection that develop into nILC2-like cells or ILC3-like cells and contribute to immunity to both helminths and fungi.