Parasitic Infections and Inflammatory Diseases

The mammalian immune system is continuously exposed to infectious microorganisms as well as innocuous substances in the environment. Depending on the genetic makeup, the innate and adaptive immune responses develop and determine the frequency and the course of infectious diseases. The immune response to an infection is initiated by molecular recognition of damage-associated patterns (DAMPs) by receptors of the innate immunity, that, most of the time, occurs as an inflammatory reaction (Turvey & Broide, 2010). The inflammation associated to parasite organisms is a complex reaction of the vascular tissues against infection, exposition to toxins or cellular injury involving extravascular accumulation of plasmatic proteins and leukocytes, as well as production of cytokines from the injured tissue. It is an essential component of multifactorial pathogenesis involved in different diseases (Scrivo et al., 2011). The acute inflammation is a common result of innate immune response; however local immune adaptative factors can also promote inflammation (Lukic et al., 2009). The morphologic transformations and functional characteristics of immunological responses and consequently, of the inflammatory processes intend to destroy, to dilute or to isolate the harmful agent. Virtually, all the acute or chronic diseases are lead or modulated by the inflammation. Although the inflammation serves to a protective function in the control of parasitic infections and promotion of tecidual repair, this can also cause injury and illness itself. Schistosomiasis is an exemple of parasitary disease caused predominantly by the host immune response to schistosome eggs (ova) and the granulomatous reaction they evoke (Burke et al., 2009). In some cases, the inflammation can even persist after the removal of the infectious agent, contributing to the chronic inflammation (Vodovotz et al., 2009). Amongst the various infectious agents, helminth parasites are regarded as master manipulators of the host immune system, often inducing a long-lasting asymptomatic form of infection. Parasitic worms can establish and reproduce in mammalian hosts, switching off the inflammatory immune response and inducing a tolerant response to parasite antigens. The time of duration and the intensity of the inflammatory agent determine different degrees or phases of transformation in tissues (Zaccone et al., 2006).