Abstract
This paper describes the characterization of the skin reactive substances from the horse-fly, Tabanus iyoensis. 1. Strongly skin reactive substances were extracted from the thorax and the abdomen of adult female bodies. Activities both from the thorax and the abdomen distributed similarly in the further fractionation process, i.e. the gel filtration by various types of Sephadex and the chromatography by ionexchange Sephadex. 2. The active substances seemed to be non-dialyzable proteins which, in respect to the molecular weight, were subdivided into 2 categories, one having the M. W. of more than 200,000 and the other the M. W. of 50,000 to 100,000. This, with the results of the ion-exchange chromatography, suggests that several substances rather than a single one, which are not very toxic themselves, are related to the human skin reaction. 3. The agar gel diffusion between the abdomen extracts and the corresponding rabbit antiserum (an active fraction after the G-25 gel filtration was used for immunization) revealed at least 2 lines, of which the main line located toward the antibody side seemed to be unrelated to the skin reaction. In the experiments with the absorbed antiserum, however, the other line disappeared when the skin reactivity (activity L) was present in the fraction used for the absorption, indicating that there may be a close connection between them. 4. Neither a hemolytic substance observed in the abdomen extracts nor a pink-colored substance in the thorax extracts having an absorption maximum at 410mμ was related to the skin reactivity.
