Specific allergic sensitsation to filarial antigens in tropical eosinophilia syndrome.

Reaginic antibodies to antigens from the human filarial parasites Wuchereria bancrofti and Brugia malayi and the animal parasite Dirofilaria immitis were studied by histamine release from basophils in 7 patients with tropical eosinophilia (T.E.) and 18 patients with other manifestations of filarial infection (lymphatic changes or symptomless microfilaraemia). All the patients had antibodies to all three filariae but T.E. patients were more highly sensitised. T.E. patients responded more to antigens from microfilariae than did patients with non-T.E. filariasis and responded more to microfilarial antigens from the human parasites than to those from the animal parasite. These findings support the view that T.E. is a form of occult filariasis which results from host hypersensitivity to the microfilarial stage of parasites which, in other individuals, cause the more common lymphatic manifestations of filarial disease.