Functional versus quantitative comparison of IL-1β from monocytes/macrophages on biomedical polymers

Studies utilizing a quantitative assay, radioimmunoassay, and a biological activity assay, the murine thymocyte proliferation assay, to analyze IL-1 beta cytokine production by monocytes/macrophages on biomedical polymers have been carried out. Results indicate that the quantitative analysis of IL-1 beta on biomedical polymers and protein-adsorbed biomedical polymers is not indicative of and does not correlate with the results of the biological activity assay. IL-1 beta secreted from human monocytes/macrophages on Biomer, polydimethylsiloxane (PDMS), Dacron, polyethylene, expanded polytetrafluoroethylene, and control polystyrene with and without the preadsorption of physiological concentrations of human IgG, fibrinogen, and/or fibronectin was assayed. Quantitative levels of IL-1 beta suggest a greater functional response than that observed in the biological thymocyte proliferation assay when the polymers were studied directly or preadsorbed with IgG. On the other hand, preadsorption with fibrinogen or fibronectin resulted in high functional activity for IL-1 beta with low quantitative levels of IL-1 beta. The lack of correlation between the functional and biological activity assays suggests the presence of other cytokines or antagonists which modulate the biological activity of IL-1 beta.