Introduction: Interactions Between the Immune System and Parasites Special Issue

Parasitism, in general, means a relationship between two organisms in which 'one organism benefits at the expense of the other' (https://www.britannica.com). In the long term, the benefiting organism, called the parasite, may have the ability to manipulate the other organism, called the host. Humans have evolved under the pressure of unicellular protozoan and multicellular metazoan (worm) parasites. A recent World Health Organization report suggests that about 1.5 billion humans are infected with worms and that 250 million humans are infected with protozoan parasites in total causing about 1 million deaths per year (http://www.who.int/features/2017/year-review/en).