Studies on Immunological Air Pouch Inflammation in the Rat

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Abstract
The development of a novel immune-based model of inflammation in the subcutaneous air pouch of the rat is described. Rats were sensitized by injection with methylated bovine serum albumin emulsified with Freund’s complete adjuvant and challenged 14 days later by injection of heat-aggregated antigen in saline into a 6-day subcutaneous air pouch. Time course studies revealed a peak polymorph cell infiltration at 24 h with no exudate formation, followed by a separate mononuclear cell response, rapid exudate formation, and granuloma formation over the 2- to 7-day period. Separate peaks of increased vascular permeability were observed in the acute and chronic phases of the response. This reaction was considered to be an example of delayed-type hypersensitivity based on its extended time course, the characteristic time course of oedema formation in footpad-challenged rats, and the failure of serum from sensitized rats to elicit a reversed passive Arthus-type reaction. The sensitization schedule was also shown to enhance the acute inflammatory response to carrageenan. In addition, the ‘flare-up’ reaction to secondary antigenic challenge was investigated in 7-day postchallenge lesions.