ENHANCEMENT OF CRYSTAL-INDUCED NEUTROPHIL RESPONSES BY OPSONIZATION OF CALCIUM PYROPHOSPHATE DIHYDRATE CRYSTALS

Objectives-Little is known about the effect on crystal induced neutrop hil responses of the opsonisation of calcium pyrophosphate dihydrate ( CPPD) (triclinic) crystals with components of serum and plasma. The pu rpose of this study was to determine the effects of precoating CPPD cr ystals with plasma, serum, complement depleted serum, and IgG on a ful l range of crystal induced neutrophil responses (calcium mobilisation, chemiluminescence, superoxide anion production, non-cytolytic lysosom al enzyme release, and leukotriene synthesis). Methods-Crystals were p recoated with IgG, serum, plasma, or complement depleted serum (heated at 56-degrees-C), incubated with neutrophils and the responses monito red with time. Measurement of the extent of neutrophil association wit h crystals was based on monitoring the decrease in fluorescence intens ity of supernatants when crystals and diphenyl-hexatriene labelled neu trophils were allowed to settle under gravity. Results-Precoating CPPD crystals with IgG, plasma, and serum significantly enhanced chemilumi nescence, superoxide anion generation, increases in cytosolic free cal cium levels, and non-cytolytic lysosomal enzyme release by neutrophils compared with uncoated CPPD crystals. The enhancement of neutrophil r esponses by crystals coated with complement depleted serum was less pr onounced. The increased neutrophil responses induced by CPPD crystals coated with IgG might have been due to the observed increase in the as sociation of IgG coated crystals with neutrophils. Conclusions-These d ata show that there is a marked potentiation of all neutrophil respons es to IgG, plasma, and serum coated CPPD crystals. It is suggested tha t the adsorption of synovial fluid proteins, including IgG and C3b, to CPPD crystals in vivo, results in the opsonised crystals becoming a p otent neutrophil stimulant and inflammatory agent,