Eosinophilia is frequently observed
after treatment of patients with
infections due to parasitic helminths. For definition of the characteristics and causes of post-treatment eosinophilic responses, 47 patients with Bancroft's
filariasis, who were treated with
diethylcarbamazine, and eight patients with
schistosomiasis mansoni, who were treated with
niridazole, were studied. After
therapy for eight days, both groups developed significant (P less than 0.05) increases in their levels of
eosinophilia, which peaked in two to four weeks. Maximal levels averaged two and one-half to three time the levels before treatment. Before
therapy the number of circulating eosinophils was unrelated to intensity of
infection in both groups, but
after treatment, when the same relationship was examined in the larger group (the patients with
filariasis), the degree of post-treatment
eosinophilia was significantly correlated with the patients' worm burdens before treatment (r = 0.727; P less than 0.001). Thus, treatment of helminthic
infections can provide a unique opportunity for studying eosinophil responses of humans to graded doses of
antigen and has shown that acute responses are determined quantitatively by the amount of
antigen initially presented to the host.