以55%percoll配製之連續梯度分離家蠶血球，可得穩定性高及相當純度之原生質血球(PL)。以掃描電子顯微鏡及位相差顯微鏡觀察，家蠶之原生質血球外型為圓形或紡錘形，可迅速擴展開來而有多種型態變化。PL擴展行為之過程為(1)血球延伸拉長與接觸面形成絲狀偽足，(2)在偽足間之細胞膜擴張形成板狀偽足，(3)PL極度扁平化。家蠶顆粒血球內容物存有促進PL伸展偽足之黏附因子，此因子會促進PL擴展開來黏附一起而參與包圍作用。此等黏附因子的作用在細胞性防禦反應中具有重要之功能。 Pure plasmatocytes (PL) were isolated by continuous density gradients of 55% hyper-osmo-ic percoll. Obsenation with phw contrast microscope and SEM showed these PLs were ovoid Ir spindle-shaped. In response to cell-substratum contact, these PLs underwent a serious of dis-inct morphological changes including 1). elongahon of PLs 2). the production of filopodia and lamella. 3). fully spreading PLs with a Aattened morphology. In vitro spreading assay showed the presence of cellular adhesive factors promoting the ex-tension in PLs. This adhesive factor could mediate PL spreading and cause PL attaching to each other to achieve encapsulation, thus it is suggested that this adhesive factor play an important role in cellular defense reaction.