Dr. Kassai Tibor szerk.: Parasitologia Hungarica 2. (Budapest, 1969)
vétlen szerepet játszanak a férgekkel szembeni immunitásban. Rats immunologically tolerant to N. brasiliensis infection may respond with either a primary-type or a secondary-type reaction to homologous reinfection when adult. The course of the challenge infection, as a rule, is similar to that of a primary reaction. Elimination of the worms is, however, incomplete and a tolerant-type (small, stable, sexually active with about 50 jfi of females) residual population survives within the host. Tolerant hosts reinfected during the course of their immunological maturation or, presumably, young rats given a single but sufficiently massive early infection (1000 larvae), acquire immunity to later reinfections (secondary-type reaction). Even so the relative equilibrium of the host-parasite relationship characteristic of the state of tolerance is maintained, allowing a permanent, low-grade egg production by a tolerant-type residual worm population (double induction). This phenomenon may be of relevance in the epidemiology of helminth diseases. The heterohaemolysin-producing capacity of Nippostrongylustolerant rats induced by the injection of sheep red blood cells during adulthood was similar to that of non-tolerant controls. No correlation was found between the level of circulating homocytotropic (reagin-type ) antibody titre of individual rats, measured by the homologous passive cutaneous anaphylaxis (PCA) test and their immunological status (tolerant, immune, doubtful) as judged by worm recoveries. Immune rats often possess little or no reaginic antibody titre, while the serum of tolerant rats may contain large amounts of homocytotropic antibodies. ' These observations cast further doubt on the direct role of reagin-type antibodies in helminth immunity. (Helminthological Research Lab. Veterinary Univ., Budapest ,VII . Rottenbiller u. 50.)
