Although haemocytes of the forest pest lepidopteran, Malacosoma disstria (L.) have been studied, the physico-chemical factors and signalling components affecting their non-self activities have not been examined. Both the ameboid and stellate forms of plasmatocytes and the granular cells from fifthinstar larvae adhere best to glass slides with phosphate-buffered saline (PBS), with maximum granular cell binding within a pH range of 6.0-7.0 and plasmatocyte binding at pH 6.0. The divalent cations, calcium and magnesium, do not affect granular cell attachment. However, calcium in Galleria-anticoagulant and PBS and, to a lesser extent, magnesium in the anticoagulant, increase plasmatocyteglass contact. Based upon the use of selective type I protein kinase A inhibitor (Rp-8-Br-cAMPS) and activator (Sp-8-Br-cAMPS), active protein kinase A inhibits the adhesion of both haemocyte types. Similarly, protein kinase C inhibited by Go¨6976 enhances haemocyte adhesion whereas the enzyme activator, phorbol-myristate-acetate, impairs attachment.

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