All of 25 individuals suspected of having Wuchereria bancrofti infections gave positive intradermal reactions with a 1:8,000 dilution of an antigen prepared from Dirofilaria immitis while false positive reactions in non-infected and allergic persons were screened out by the use of this dilution. Only 4 of the 25 individuals had harbored helminth parasites other than W. bancrofti and sufficient evidence is therefore not available from our tests to indicate whether the abovementioned dilution of the antigen would satisfactorily screen out false positive reactions which might be due to these other parasites.
In some cases the injection of the 1:8,000 dilution of the antigen was followed by exacerbations of the symptoms of lymphangitis together with pain in the scrotum and inguinal glands.
Negative complement fixation tests were obtained in the above-mentioned cases with saline antigen ranging in dilutions from 1:100 to 1:1,600, although positive results were obtained in rabbits immunized with the residue from the antigen preparation. The alcoholic antigen appeared to be inferior to the saline material.
By testing 24 hours later with the D. immitis material, local passive hypersensitivity to D. immitis antigen was elicited in 4 of 6 recipients injected with the bood serum of filariasis patients.
Seven of 12 rabbits died while being immunized to the residue obtained from the antigen preparation, a fact which would seem to indicate that the adult worms contain some toxic substance.