Self-organization of IgE immunoglobulins on phospholipid films

Mouse monoclonal IgE anti-2,6-dinitrophenyl antibody (clone SPE-7) crystallizes in two dimensions when bound to a phospholipid monolayer or bilayer that has been combined with the hapten 2,6-dinitrophenyl groups. The two-dimensional lattice exhibits considerable local disorder, but long-range order is maintained over many unit cells of the lattice. The crystallization of IgE on the films is sensitive to IgE concentration in bulk solution. The optimum appears to be in the range 100-200 micrograms/ml. The crystallization tendency is diminished at pH lower than pH 6.5, and the crystals 'melt out' at a rather low temperature; no crystals were observed for 37 degrees C and above. The crystal growth rate is very much lower than was observed for monoclonal IgG1 anti-2,6-dinitrophenyl antibody. Finally, the IgE lattice is very different from the two-dimensional lattice formed by IgG1: the hexagonal lattice unit cell is smaller and has an open structure.