SILICA BEADS INDUCE CELLULAR AND HUMORAL IMMUNE-RESPONSES IN GALLERIA-MELLONELLA LARVAE AND IN ISOLATED PLASMATOCYTES, OBTAINED BY A NEWLY ADAPTED NYLON WOOL SEPARATION METHOD

Intrahaemocoelic injection of silica beads into Galleria mellonella (w ax moth) larvae provoked strong cellular and humoral reactions similar to those normally occuring during an antibacterial defence. The cellu lar reactions of the haemocytes-investigated by light and scanning ele ctron microscopy-comprised degranulation of granular cells and phagocy tosis by plasmatocytes. The humoral responses-measured in cell free ha emolymph as the increase of antibacterial activity against Echerichia coli K12 D31 and of lysozyme activity against Micrococcus luteas cell walls-were significantly enhanced in comparison to controls. Only hydr ophylic but not hydrophobic silica beads provoked strong reactions. Pl asmatocytes (PLs), the main phagocytic haemocytes of G. mellonella, we re isolated by using a newly adapted nylon wool column technique. PL m onolayers, prepared from isolated cells, exhibited a high purity by co nsisting of at least 90% PL. Scanning electron microscopy studies reve aled that 64% of the isolated PLs showed phagocytic activity against t he sterile silica beads in vitro. Intrahaemocoelic injection of supern atants from monolayers with phagocytosing plasmatocytes into naive lar vae led to a clearly higher antibacterial activity against E. coli in haemolymph of recipients than the injection of supernatants from monol ayers with non-phagocytosing cells. The earlier supposition that haemo cyte-released factors induce the humoral immune response is further su pported by these results.