Humoral factor activating the Sarcophaga lectin gene in cultured fat body

On culture of the fat body of Sarcophaga peregrina (flesh fly) larvae in modified Grace's medium, the Sarcophaga lectin gene was activated only when the medium was supplemented with larval hemolymph. The expressions of the genes for the storage protein and the sarcocystatin A were not affected by supplementing the medium with the hemolymph. Thus the hemolymph contained a factor that specifically activated the Sarcophaga lectin gene. This factor seemed to be a heat-stable, low molecular weight compound that was probably not a peptide, and to activate genes in the fat body for defense proteins that are known to be expressed in response to injury of Sarcophaga larvae.