Effect of disruption of plasmatocyte microfilaments on encapsulation in vitro.

Very little is known about the functional basis of plasmatocyte motile behaviour. In this study we documented the effects of cytochalasin B (CB) on the cytoskeletal organisation and behaviour of plasmatocytes during spreading on a planar surface in vitro, and during in vitro encapsulation. CB produced a reversible and dose-dependent effect on the rate of plasmatocyte spreading. Moreover, incubation of fully spread plasmatocytes in CB caused their microfilaments to coalesce and the cells to arborise and eventually revert to the less adhesive spindle-shaped morphology characteristic of free plasmatocytes in circulation. The use of cytochalasins B and D on haemocytes encapsulating cotton fibre loops in vitro resulted in the development of abnormally flocculent capsules. The data demonstrate the importance of microfilament-dependent PL motility, both during the secondary "compaction phase" of encapsulation and in the laboratory manifestation of this process, spreading on a planar substratum.