Immunoreactivity in pulmonary echinococcosis. 2. Evaluation of antibody response.

The part played by certain factors in determining the antibody response in pulmonary echinococcosis has been studied. Five immunodiagnostic procedures were used-complement fixation, latex agglutination, bentonite flocculation, passive haemagglutination, and intradermal tests-and parasitological and pathological examinations were carried out. The number of hydatid cysts had only a small influence on the qualitative nature of the immune response while the quantitative effect was considerable. The immune response did not vary significantly in relation to the size of hydatid cysts but it was affected by changes within the cysts and the surrounding lung tissue. In patients with cysts full of clear hydatid fluid the proportions with negative results and relatively low antibody titres were highest. In these patients the size of hydatid cyst appeared to be significant-the smaller the size, the lower the antibody level. The immune response is weak or completely absent when the hydatid cyst has a thick fibrous capsule. When suppurative changes are present in the hydatid fluid and/or in the fibrous capsule, and when there is inflammatory involvement of the surrounding lung tissue an easily detectable immune response may be seen at an early stage, sometimes even with a high antibody level, but later it usually decreases and may disappear completely. A hypothesis for the explanation of immunological reactivity in pulmonary hydatid disease is discussed.