TREATMENT OF L(2)MBN DROSOPHILA TUMOROUS BLOOD-CELLS WITH THE STEROID-HORMONE ECDYSONE AMPLIFIES THE INDUCIBILITY OF ANTIMICROBIAL PEPTIDE GENE-EXPRESSION

Insects rely on both humoral and cellular mechanisms to defend themsel ves against microbial infections, The humoral response involves synthe sis of a battery of potent antimicrobial peptides by the fat body and, to a lesser extent, by blood cells. The cellular response on the othe r hand consists of phagocytosis of small microorganisms and melanizati on and encapsulation of larger parasites. The l(2)mbn cell line, estab lished from tumorous larval hemocytes, represents a system of choice t o dissect the molecular events controlling cellular immunity. We repor t here that l(2)mbn cells can be efficiently induced to differentiate in adherent, macrophage-like cells by treatment with 20-hydroxyecdyson e. Ecdysone treatment increases both the phagocytic capacity of l(2)mb n cells and their competence to express antimicrobial genes in respons e to immune challenge. We also report that expression of several regul atory molecules thought to be involved in the immune response is up-re gulated by ecdysone in l(2)mbn cells. (C) 1997 Elsevier Science Ltd. A ll rights reserved.