Fig. 2.

Helminth EVs and myeloid cells.

Helminth extracellular vesicles are taken up by myeloid cells, interfering with innate defense pathways. (1) EVs from H. polygyrus are able to downregulate the IL-33 receptor subunit ST2, reducing their ability to respond to this cytokine. (2) EVs from B. malayi contain miRNAs that target components of the mTOR signalling pathway, downregulating it. These effects, as well as others yet characterised, combine to alter the activation state of macrophages. (3) EVs from S. japonicum and B. malayi induce M1 polarisation, whereas H. polygyrus EVs inhibit both M1 and M2 polarisation. (4) Helminth EVs interfere with the expression of components involved in antigen presentation and lymphocyte activation. E. granulosus EVs cause a decrease in MHC II in dendritic cells. E. granulosus and F. hepatica EVs both increase the costimulatory marker CD86 in dendritic cells. (5) Antibodies raised against helminth EVs prevent their action, either by preventing uptake altogether, or leading to their uptake into a degradative pathway in the lysosome.

Images are adapted from Servier Medical Art by Servier (http://smart.servier.com/) and modified by the authors under the following terms: Creative Commons Attribution 3.0 Unported (CC BY 3.0).