The immune response to pertussis in the 6-day air pouch: a model of chronic synovitis.

We have developed a model of prolonged immunological inflammation in the rat which has a structural resemblance to the synovial changes in rheumatoid arthritis. Pertussis vaccine was injected into 6-day-old subcutaneous air pouches in animals previously sensitized with pertussis vaccine. The resulting inflammatory response persisted up to 30 days. Examination of exudates showed a wave of polymorphonuclear leucocytes over a 13-day period followed by a mononuclear cell predominance up to 30 days. Histologically, an early polymorphonuclear cell infiltration was followed by the formation of a lining layer of large eosinophilic mononuclear cells, together with deep collections of lymphocytes and plasma cells. Concentrations of the acute-phase reactant alpha 1-glycoprotein, in both serum and exudate, peaked at 3 days. This suggests that the local production of interleukin I in this type of tissue reaction is more closely related to the acute inflammatory phase than to more chronic interactions between monocyte derived cells and lymphocytes.