Encapsulation of foreign particles in vitro by separated blood cells from crayfish, Astacus leptodactylus

Abstract

Blood cells from Astacus leptodactylus were separated by density gradient centrifugation and used to study in vitro encapsulation of different objects. Each of the three different populations of haemocytes responded differentially to the foreign particles tested (fungal spores of Aspergillus niger, or ion exchange particles with neutral, positive or negative surface charges). The semigranular cells encapsulated all foreign objects tested, regardless of origin or surface charge, and the capsules developed within 15 h to very dense and tight structures. The granular cells only aggregated around the fungal spores, but no dense capsules were formed. Only a very weak association between granular cells and the beads could be observed. The hyaline cells could not encapsulate any foreign particle, not even if incubated together with granular or semigranular cells. Capsule formation was associated with degranulation of the cells since encapsulation was either inhibited or delayed if the cells were incubated with compounds known to affect degranulation in crayfish granular and semigranular cells, such as A 23187, SITS, EDTA, LPS or laminaran.