ENHANCEMENT OF THE MACROPHAGE OXIDATIVE BURST BY IMMUNOGLOBULIN COATING OF RESPIRABLE FIBERS - FIBER-SPECIFIC DIFFERENCES BETWEEN ASBESTOS AND MAN-MADE FIBERS

The ability of long amosite asbestos fibers (LFA), vitreous fibers (MM VF 21 and CODE 100/475), and ceramic fibers (silicon carbide and RCF 1 ) to stimulate superoxide production in isolated rat alveolar macropha ges is examined. The cells were exposed to both naked fibers (uncoated ) and fibers coated with rat immunoglobulin (IgG), a normal component of lung lining fluid. The affinity for IgG of the various fibers was a ssessed by quantifying the binding of I-125-labeled IgG onto the fiber surface. Naked fibers stimulated a modest release of superoxide anion from alveolar macrophages, which was not obviously dose dependent. Wh en IgG was adsorbed onto fibers of MMVF 21 and RCF 1, there was a dram atic increase in superoxide release, which correlated well with their high affinity for IgG. IgG-adsorbed code 100/475 and silicon carbide w hiskers (SiCW) stimulated only modest superoxide release, and the fibe rs showed a correspondingly poor affinity for the opsonin. Conversely, the adsorbed fibers of LFA, generated a dramatic increase in superoxi de release from the macrophages, despite a relatively poor adsorption of IgG. This study demonstrates the potential for components of the lu ng lining fluid to modify the response of alveolar macrophages to resp irable natural and man-made fibers. It also draws attention to fiber-s pecific differences in adsorptive capacity and subsequent biological a ctivity between these fiber types in vitro and, by implication, in viv o.