Modification of asbestos bioactivity for the alveolar macrophage by selective protein adsorption

The bioactivity of an inhaled particulate is likely to be influenced significantly by the adsorption of proteins and lipids from the fluid lining the respiratory tract. We have shown previously in vitro that the presence of immunoglobulin G, a protein constituent of the lining fluid, significantly and specifically enhances the response of the guinea pig alveolar macrophage to chrysotile, but not crocidolite, asbestos. In order to understand the differential response of the guinea pig alveolar macrophage to chrysotile and crocidolite, as well as to obtain a better understanding of the factors that determine the adsorption of proteins onto asbestos, we have quantitated the adsorption of model proteins, including IgG, onto asbestos. The apparent surface density to which a given protein adsorbed was found to be influenced significantly by the surface charge of the asbestos, by the net protein charge, i.e., its isoelectric point (pI), and most dramatically, by the presence of other proteins. Thus, for example, even when guinea pig IgG (gpIgG; pI approximately 8.5) and bovine serum albumin (BSA; pI = 4.8) were present together at a high molar ratio of BSA to gpIgG, gpIgG was selectively adsorbed on negatively charged crocidolite asbestos. An analogous result was found for the adsorption of gpIgG and cytochrome c (CYT; pI = 10) on positively charged chrysotile asbestos, i.e., even at high molar ratios of CYT to gpIgG, gpIgG was selectively adsorbed. This latter result provides an explanation for the differential bioactivities of chrysotile and crocidolite asbestos previously noted in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)