Immune enhancement of granuloma formation as an experimental model for the pannus of rheumatoid arthritis.

The pannus of rheumatoid arthritis is a proliferating mass of various cells and tissues, including follicles of lymphoid cels, and is the major agent of destruction of the surrounding structural tissues. Infiltrating lymphocytes are thought to be the prime stimuli for the growth of the pannus, through the secretion of of lymphokines. In contrast to this high turnover, destructive rheumatoid granuloma, most commonly used experimental granuloma models are of the non-immune, low turnover variety and thus give a rather poor reflection of clinical conditions. A model has been developed in our laboratory in which lymph node cells are removed from Freund's complete adjuvant sensitized rats and injected into sponge implants in normal syngeneic recipient animals, leading to enhancement of granuloma formation. This response has been characterized and shown to be related to lymphocyte activation and to the sensitivity of rats to polyarthritis induction. The lymphocyte transfer model may be useful in studying the action of drugs on lymphocyte mediated chronic inflammatory responses and the principle of lymphocyte transfer may be applied to other hypersensitivity granuloma models.