ENCAPSULATION OF FOREIGN TARGETS BY HEMOCYTES OF THE MOTH PSEUDOPLUSIA-INCLUDENS (LEPIDOPTERA, NOCTUIDAE) INVOLVES AN RGD-DEPENDENT CELL-ADHESION MECHANISM
Ll. Pech et Mr. Strand, ENCAPSULATION OF FOREIGN TARGETS BY HEMOCYTES OF THE MOTH PSEUDOPLUSIA-INCLUDENS (LEPIDOPTERA, NOCTUIDAE) INVOLVES AN RGD-DEPENDENT CELL-ADHESION MECHANISM, Journal of insect physiology, 41(6), 1995, pp. 481-488
We tested the hypothesis that an insect immune response, encapsulation
, involves an RGD-dependent cell adhesion mechanism by examining the e
ffects of the tetrapeptide RGDS on hemocyte spreading and encapsulatio
n, Soluble RGDS at concentrations of 0.5-2 mM inhibited the spreading
of the primary encapsulating hemocyte, the plasmatocyte, on the surfac
e of plastic tissue culture plates. At concentrations of 5-10 mM, the
spreading of granular cells was also inhibited, RGES did not inhibit p
lasmatocyte or granular cell spreading, indicating that the effect was
specific for RGDS. RGDS-Sepharose beads were encapsulated by hemocyte
s in vitro, whereas RGES-Sepharose beads were not. Furthermore, solubl
e RGDS, but not RGES, inhibited in vitro encapsulation of RGDS-Sepharo
se. When injected into the hemocoel of P. includens larvae, RGDS-Sepha
rose was encapsulated in 3 h, whereas RGES-Sepharose was not encapsula
ted until 24 h. The only hemocyte morphotype to encapsulate RGDS-Sepha
rose was the plasmatocyte. Lastly, RGDS, but not RGES, inhibited plasm
atocyte spreading in response to cell-free plasma, These results indic
ate that the molecular basis of cell adhesion mediating hemocyte sprea
ding and encapsulation in insects involves cell adhesion molecules con
taining the RGD recognition sequence.