In vitro fluorescent antibody studies on Ascaris lumbricoides and Ascaris suum

Abstract

Abstract 1. 1) The immunology of Ascaris suum and Ascaris lumbricoides was studied in vitro by means of the fluorescent antibody technique. Globulin was labelled with fluorescein isothiocyanate and the direct, indirect and combined methods of staining were used. 2. 2) A cross-reaction between the two ascarids was demonstrated by the fluorescence of decoated eggs of A. lumbricoides after their immersion in labelled rabbit anti-pig Ascaris immune globulin. Decoated eggs did not fluoresce after their exposure to labelled rabbit normal globulin. Fluorescence of intact eggs in the same normal globulin was considered non-specific. Circumoral precipitates did not form in either the homologous or heterologous immune systems. 3. 3) Cross-reactions with third-stage larvae were also observed when pig Ascaris larvae were placed in serum from monkeys immune to A. lumbricoides , and after larvae of this species were exposed to antisera from rabbits immune to the pig Ascaris . Fluorescent antibody was incorporated into precipitates at the mouth, excretory pore, anus and on the cuticle of living larvae. In most instances the cuticle also fluoresced green. The digestive tract did not stain. The specificity of staining was confirmed by the absence of both precipitates and fluorescence when the larvae were placed in normal serum. 4. 4) The results indicate that i), embryonated Ascaris eggs are antigenic; ii), in third-stage Ascaris larvae the antigenic sites are located at the natural orifices and cuticle; and iii), the worm eggs and third-stage larvae of A. lumbricoides and A. suum share common antigens. 5. 5) It has not been possible, so far, to differentiate the two worms by the use of the fluorescent antibody technique.