Monoclonal Antibody MS13 Identifies a Plasmatocyte Membrane Portein and Inhibits Encapsulation and Spreading Reactions of Manduca sexta Hemocytes

摘要

Lepidopterans generally can successfully defend themselves' ~ against a variety of parasites or parasitoids. One mechan:ism- they use is to encapsulate the invader in many layers of hemocytes. For encapsulation to occur, the hemocytes must.at- tach to the foreign material, spread, and adhere to each other.The molecules that mediate these processes are not known. One method to identify proteins potentially necessary for adhesion,spreading, and, thus, encapsulation is to use monoclonal anti- bodies that interfere with these functions. In this paper, we report that a monoclonal antibody against Manduca sexta plasmatocytes effectively inhibited encapsulation of synthetic beads in vitro and in vivo. Furthermore, it inhibited plasma- tocyte spreading in vitro. Other anti-hemocyte antibodies did not have these effects. The plasmatocyte-specific monoclonal antibody, mAb MSI3, recognized a protein of approximately 90,000 daltons as indicated by Westem blot analysis of hemocyte lysate proteins. The epitope recognized by mAb MS13 was present on the exterior surface of plasmatocytes. Using indi- rect immunohistochemistry with hemocyte-specific antibodies, we also determined that during encapsulation plasmatocytes were the first cells bound to latex beads and later layers con- sisted of both plasmatocytes and granular cells. Arch. Insect Biochem. Physiol. 45:95-108, 2000.