Protective immune mechanisms in helminth infection

Abstract

Helminth parasites cause chronic disease in billions of people, however, the immune response associated with helmith infection can also reduce the severity of certain harmful inflammatory autoimmune and allergic diseases. Studies of tissue-dwelling parasites in murine models reveal the development of T helper 2 (T_H2)-type granulomas consisting of cellular infiltrates that resemble T_H1-type granulomas; however, the cells are activated differently and have distinct functions. The T_H2-type response can affect host protection by mediating helminth expulsion or by controlling otherwise pathological inflammatory responses that are driven by T_H1 and T_H17 cells. T_H2 cells are the primary source of T_H2-type cytokines but innate cells can also produce these cytokines. T_H2-type cytokines, including interleukin-4 (IL-4) and IL-13, orchestrate a potent T_H2-type response by direct stimulation of both bone-marrow-derived and non-bone-marrow-derived cell populations. A similarly complex and multi-faceted T_H2-type response is elicited following infection with a wide variety of helminths; however, only certain components of this broad response are effective against a particular species. The discovery of new effector cell types and molecules contributing to the host protective T_H2-type response provides additional targets for the development of novel therapies against helminths.