Encapsulation is the immune response in which insect hemocytes attach to a large metazoan parasite, thus forming a cellular capsule around the foreign invader and rendering it inactive. In the moth Manduca sexta (Sphingidae: Lepidoptera), the two hemocyte types involved in encapsulation are plasmatocytes and granulocytes. Monoclonal antibodies to M. sexta hemocytes were developed. Monoclonal antibody MS34 specific to plasmatocytes was found to inhibit encapsulation. Immunoaffinity purification with MS34 isolated a protein approximately 100 kD in size. Edman degradation of trypsin fragments of this protein revealed short peptide sequences which were used to construct degenerate primers. RT-PCR with hemocyte mRNA produced an 803 bp DNA product. This DNA sequence encodes a protein highly similar to the b-subunit of integrins which are transmembrane proteins mediating cell adhesion. These results suggest that an integrin expressed on the surfaces of plasmatocytes is involved in hemocyte adhesion during encapsulation.
Species 1: Lepidoptera Sphingidae Manduca sexta (tobacco hornworm)
Keywords: encapsulation, integrin
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