Colophony: an in vitro model for the induction of sensitization

Background The potential of colophony fumes from soldering flux to induce a sthma has been known since the 1970s, however, no direct in vitro or in viv o evidence has been reported. The present study investigated the potential of colophony to stimulate human phagocytic cells to produce reactive oxygen species. Methods The human cell line HL-60 was differentiated to produce cells with a monocyte-like and a neutrophil-like phenotypes. A number of procedures we re used to confirm the phenotype of these differentiated cells including mo rphology, esterase activity, flow cytometry and phagocytosis. The potential of colophony to stimulate human phagocytic cells to produce reactive oxyge n species was monitored using flow cytoenzymology. Results We were able to show that intracellular peroxide levels were increa sed in both monocyte-like and neutrophil-like cells, but not in undifferent iated HL-60 cells following the addition of colophony. Conclusions The resin acid epoxides and hydroperoxides which have been sugg ested to be sensitizers in contact allergy, are degraded during the solderi ng process. However, conditions for the oxidation of colophony may occur in vivo as a result of the colophony-induced oxidative burst from neutrophils and monocytes. These oxidation products may then interact with body protei ns to further initiate immune responses. Therefore for the preparation of l ow molecular weight chemical (LMWC)-protein conjugates, consideration must be taken to determine whether the LMWC is undergoing a reaction in vivo bef ore it is interacting with body proteins.