Influence of blood and synovial fluid immune complexes of patients with rheumatoid arthritis on production of nitric oxide and growth and viability of chondrocytes

Objective, To determine whether blood and synovial fluid (SF) immune comple xes (IC) of patients with rheumatoid arthritis (RA) influence the productio n of nitric oxide (NO) and growth and viability of chondrocytes. Methods. IC were precipitated and IgM and Ige were determined in the precip itates by ELISA and nephelometry, respectively. Primary cultures of bovine articular chondrocytes were incubated with the IC precipitates. After 48 h NO was determined as nitrite. After 7 days, growth was determined by incorp oration of tritiated thymidine and viability was detected by neutral red up take. Results. Patient sera were positive in 8/12 for IgM IC and 9/12, for IgG IC , and 1/8 control sera was slightly positive for IgM IC, Seven of 12 SF sam ples were IgM IC and 10/12 IgG IC positive. With and without additional int erleukin 1 alpha (IL-1 alpha) stimulation, NO production by chondrocytes wa s significantly higher with SF IC precipitates than with control serum prec ipitates (p = 0.03, p = 0.04, respectively). NO production by chondrocytes that were not stimulated with IL-1 alpha was significantly increased with S F IC precipitates compared to RA serum IC precipitates (p = 0.03). SF IC si gnificantly inhibited growth compared to control serum precipitates (p = 0. 04) and RA serum IC (p = 0.012). Neutral red uptake by chondrocytes was sig nificantly decreased when incubated with RA serum IC in comparison with con trol serum IC (p = 0.012) and SF IC (p = 0.006). With and without additiona l IL-1 alpha stimulation, NO production by chondrocytes after incubation wi th:SF derived IC was positively correlated to the Ritchie score (r = 0.8, r = 0.7, respectively) and the number of swollen joints (r = 0.8, r = 0.6, r espectively). Conclusion. These results support the hypothesis that, especially in active RA, SF derived IC stimulate NO production and inhibit chondrocyte growth.