CONCEPTS AND MECHANISMS OF RESISTANCE IN HELMINTHIC INFECTIONS

The relations that exist between the helminths and their hosts cannot be divided into specific groups. Nevertheless, it is desirable that some classification of these relations, together with clear-cut definition of terms, be widely accepted in order that the subject may be discussed intelligibly. A tentative classification is suggested, which distinguishes between (i) compatibility and incompatibility, which refer only to the host environment as it exists before invasion by the parasite; (ii) resistance, of various kinds and degrees, which refers to the reaction of the environment to the presence of the helminth; and (iii) tolerance and intolerance, which refer to the reaction of the environment to the effects of the helminth.