INVIVO DISTRIBUTION OF IMMUNE PROTEIN SCOLEXIN IN BACTERIA-INJECTED MANDUCA-SEXTA LARVAE

The Manduca sexta larva-specific immune protein, scolexin, was isolate d and (CH3)-C-14-labelled by reductive alkylation. The influence of th e bacterium Streptococcus faecalis on the hemocoelic distribution of t he labelled scolexin was then analyzed. During bacterial challenge, mo st of the scolexin signal was detected in association with the hemocyt e aggregations and nodules which formed; in this respect the protein s ometimes appeared to be associated with hemocytes which had phagocytiz ed bacteria, while at other times it was most concentrated in the nodu le-associated, and free, coagulum. Areas of high scolexin activity wer e sometimes detected at various sites on the surface of the fat body. The scolexin did not appear to bind directly to bacterial cells. Up to 24 hr following the injection of S. faecalis, the larvae were still c arrying out the formation of nodules; unlike the nodules of the 3 and 6 hr intervals, the nodules observed at 21-24 hr were covered with an apparently humorally derived, coagular capsule.