Immune inflammation in newly developing facsimile synovia.

The injection of air into the subcutaneous tissue of the back in rodents has previously been shown to induce a lining which closely resembles synovial lining tissue. Air pouches of different ages represent the developmental stages of such tissue. We have found that pouches of 1 day in age induced in animals previously sensitised with bovine serum albumin (BSA) respond with low numbers of infiltrating leucocytes and a small fluid exudate volume 4 h after challenge into the pouch with BSA. In contrast, 3- and 6-day-old pouch tissue when challenged with antigen responds with a greater influx of leucocytes and a larger fluid exudate. These findings suggest that the constituent make-up of the air pouch-lining tissue is important for the full expression of the inflammatory response.