Colony assay using V79 cells, the agar diffusion assay with L929 cells, and the 7-day rabbit muscle implantation test were employed to evaluate the cytotoxicity and tissue toxicity of natural rubber latex (NRL) materials. The in vivo implantation test showed that, among 13 histological parameters, thickness of inflammatory layer was the most useful index to evaluate tissue responses quantitatively. A comparison of the in vivo and in vitro parameters revealed the following correlations between the thickness of the inflammatory layer and cytotoxicity indices: Colony assay of the extracts, IC50: r = 0.80; Agar diffusion assay, Zone index: r = 0.73; Lysis index: r = 0.61. From these results, it appears that the colony assay provides a more reliable prediction of the tissue response than the agar diffusion assay.

Only 17% of mice inoculated with lethal doses of Escherichia coli survived for 5 days after the challenge. Significant antibacterial activity of PSK, a protein-bound polysaccharide, was induced when the mice were pretreated with 40 mg/kg of PSK by an intraperitoneal, subcutaneous or intramuscular route, but not by an intravenous route, 48 hr before the E. coli inoculation. Repeated oral administration of PSK for 2 weeks (20 mg/kg, 3 times per week) before E. coli inoculation was also effective. Intraperitoneal administration of PSK was most potent, inducing significant polymorphonuclear cell accumulation and generation of luminol-dependent chemiluminescence by peritoneal exudate cells, with a peak 24 hr after administration of the PSK.

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