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An assessment was made of the cellular inflammatory response to the subcutaneous implantation of sterile nitrocellulose discs and polyvinyl sponges in both normal rats and rats with adjuvant-induced arthritis. It was found that from 3 days after adjuvant injection the treated animals exhibited a reduced accumulation of inflammatory cells onto the nitrocellulose discs and that this impairment in response was not apparent until the discs had been retained for longer than 24 h. When discs were implanted after non-arthritogenic doses of adjuvant constituents or injection of brewer's yeast no effect was seen on the subsequent response. When polyvinyl sponges were used in adjuvant-treated animals a similar initial reduction in cellular accumulation was observed, which was later followed by increased cell numbers associated with enhanced granuloma formation. Differential cell counts revealed that both neutrophil and mononuclear cell types were affected. Some of the possible mechanisms involved in these observations are discussed.

Comparison of cotton wool and sponge-induced granulomas in the rat showed that collagen contents were very similar despite the different pattern of granuloma formation. There was significantly less variation of individual results in the sponge. Although collagen accounted for less than 10% of the dry weight, there was a positive correlation between the 2 parameters in both models of 9 days but only in the pellet at 15 days. Hydrocortisone treatment significantly decreased dry weight and collagen content. There was rapid cell proliferation and collagen synthesis in the sponge granuloma from Day 5, reaching a peak between the ninth and twelfth day, when DNA levels dropped and collagen increased more slowly to plateau by Day 15. Day 9 was chosen as the most suitable stage to study drug effects. Dexamethasone significantly decreased collagen synthesis whereas indomethacin and phenylbutazone did not. Soluble collagen levels were increased with beta-amino-propionitrile and d-penicillamine; a dose-related effect was obtained with d-penicillamine.