EARLY CARTILAGE DEGRADATION IN CATIONIC IMMUNE-COMPLEX ARTHRITIS IN MICE - RELATIVE ROLE OF INTERLEUKIN-1, THE POLYMORPHONUCLEAR CELL (PMN)AND PMN ELASTASE

Objective. To determine the relative role of interleukin 1 (IL-1), pol ymorphonuclear cell (PMN) and PMN elastase in early cartilage degradat ion in cationic immune complex mediated arthritis (ICA) in mice. ICA i s characterized by early production of IL-1, pronounced influx of PMN and marked cartilage degradation within one day. Methods. IL-1 was neu tralized by polyclonal antibodies against IL-1 alpha and IL-1 beta, gi ven shortly before arthritis induction. The role of PMN was studied in mice made neutropenic by whole body irradiation (750 rad). The effect of elastase was examined in beige mice with PMN deficient in elastase . Results. Neutralizing IL-1 during arthritis induction reduced PMN in filtration significantly and diminished cartilage degradation by 50%. In neutropenic mice, joint inflammation was virtually absent and carti lage proteoglycan loss was abolished. Finally arthritis was induced in beige mice. Although elastase appeared to be the dominant cartilage d egrading factor in vitro, we found no difference in cartilage degradat ion in arthritic joints of beige mice and their normal littermates. Co nclusions. Our data suggest that IL-1 is a crucial factor regulating P MN influx in ICA. The PMN are involved in cartilage degradation but a direct destructive role (e.g., by elastase) seems unlikely.