Immunoglobulins on the surface of monosodium urate crystals: an immunoelectron microscopic study

The ability of monosodium urate (MSU) crystals to bind immunoglobulins from human serum was investigated by immunoelectron microscopy. Synthetic MSU crystals were incubated with serum and then processed with an indirect immunoperoxidase technique which used primary antibodies directed against human IgG, IgA or IgM, respectively specific for Fc fragments, alpha chains, and mu chains. Results were analyzed by transmission electron microscopy on intact crystals dried on formvar coated grids, and in thin sections. Both techniques demonstrated the binding of IgG, IgA and IgM to MSU crystals and the availability of the Fc fragment of the crystal bound IgG for immunologic reactions.