DIFFERENTIAL RELEASE OF SUPEROXIDE ANIONS BY MACROPHAGES TREATED WITHLONG AND SHORT-FIBER AMOSITE ASBESTOS IS A CONSEQUENCE OF DIFFERENTIAL AFFINITY FOR OPSONIN

Objective-To investigate the ability of short and long fibre samples o f amosite asbestos to stimulate superoxide production in isolated rat alveolar macrophages, and to determine how opsonisation with rat immun oglobulin might modify this response. Methods-Macrophages were isolate d from rat lung by bronchoalveolar lavage and challenged with both ops onised and non-opsonised long and short fibres of amosite asbestos. Re lease of superoxide anions was measured by the spectrophotometric redu ction of cytochrome c, in the presence and absence of superoxide dismu tase. Results-Both long and short fibre samples of amosite asbestos wi thout opsonisation were ineffective in stimulating isolated rat alveol ar macrophages to release superoxide anions in vitro. After opsonisati on with immunoglobulin, however, a dramatic enhancement of release of superoxide anion was seen with long fibres, but not short, which confi rms the importance of fibre length in mediating biological effects. Th e increased biological activity of the long fibre sample is explained by increased binding of the opsonin to the fibre surface as, at equal mass, the long fibres bound threefold more immunoglobulin than the sho rt fibres. Conclusion-Opsonisation is an important factor in modulatio n of the biological activity of fibres at the cellular level. Differen ces in binding of opsonin to samples of fibre previously considered to be identical apart from length, suggest that surface reactivity needs to be taken into account when fibres are compared. Binding of biologi cal molecules, in vivo, may thus be an important modifying factor in t he pathological processes initiated by fibres.