Experimental chronic arthritis and granulomatous inflammation induced by Bifidobacterium cell walls

Effects of cell walls (CWs) from two almost identical strains of Bifidobact erium adolescentis were studied in rats, using three different doses. A sin gle i.p. injection of both CWs triggered a long-lasting arthritis with CW d egradation products present in the joint tissue. Histologically, the arthri tis was characterized by inflammatory cells, synovial hyperplasia, pannus f ormation and bone erosion, closely resembling human rheumatoid arthritis (R A). In addition, CWs of the other strain induced a remarkable granuloma for mation in the spleen and liver. Both CWs have the same peptidoglycan (PG) t ype A4 alpha/beta, but differ from each other in three aspects. CW of the g ranuloma inducing strain: firstly has more lysine and less ornithine in PG stem peptides; secondly is more resistant to lysozyme degradation, and thir dly is better retained in the spleen. All these in comparison to the other strain used. Such characteristics are associated with the capacity to induc e chronic arthritis, but it remains open how crucial they are for the granu loma formation.