An experimental model of pulmonary arterial granulomatous inflammation.

An experimental method to investigate pulmonary granuloma formation in the guinea pig was established. Animals sensitized to human serum albumin (HSA) and challenged intravenously with HSA covalently linked to Sepharose 2B beads developed a specific granulomatous response. This intense pulmonary arterial, focally necrotizing, but mainly granulomatous inflammatory reaction developed 5 to 7 days after the administration of the HSA-bead conjugate. Unsensitized animals did not show such extensive inflammation, but rather exhibited a typical foreign body reaction to the bead. In both the experimental and control groups, the inflammatory response was indistinguishable at 14 and 21 days. Thus the initial acute inflammatory reaction was seen only in specifically sensitized animals. On the other hand, HSA alone produced no demonstrable inflammatory lesion. These observations suggest that locally retained antigen may trigger antigen-specific T (thymus-dependent) lymphocytes to release mediators which contribute to granuloma formation.