HUMAN GALLSTONES CONTAIN PRONUCLEATING NONMUCIN GLYCOPROTEINS THAT ARE IMMUNOGLOBULINS

Objective Pronucleating nonmucin glycoproteins in human cholesterol an d black gallstones were isolated and identified. Summary Background Da ta Gallbladder bile contains nonmucin glycoproteins that are pronuclea ting of cholesterol monohydrate crystals. Little is known about the pr esence or activity of these proteins within gallstones. Methods Nonmuc in glycoproteins were isolated from single cholesterol (n = 8), multip le cholesterol (n = 8), and black pigment (n = 8) gallstones by concan avalin A lectin-affinity chromatography. The proteins were separated b y sodium dodecyl sulfate gradient electrophoresis. Western blot analys is was performed for Fab immunoglobulin fragments, and heavy chains fr om the immunoglobulin G, A, E, and M subclasses. A crystal observation time assay was performed on the combination of isolated nonmucin glyc oproteins from gallstones and isolated Fab fragments. Results Nonmucin glycoproteins of molecular weights 10, 15, 17, 22, 28, and 208 kD wer e identified in gallstones. These six nonmucin glycoproteins shortened the crystal observation time by more than 50% (p<0.01) compared with model bile. Western blot analysis confirmed the identity of the 22-and 28-kD proteins as immunoglobulin Fab fragments. These were seen in al l gallstones, irrespective of the gallstone type. The isolated Fab 28- kD fragment from the gallstones of 23 patients shortened the extrapola ted crystal observation time by 78% (p<0.01). However, commercially av ailable Fab fragments had no effect on either cholesterol crystal appe arance or growth. Conclusions Nonmucin glycoproteins that are pronucle ating for cholesterol monohydrate crystals are also found in human cho lesterol and black pigment gallstones. Fab immunoglobulin fragments we re found in all gallstones irrespective of the gallstone type. Fab imm unoglobulin fragments from gallstones shortened the crystal observatio n time but not crystal growth or total crystal content compared with m odel bile or commercially available Fab fragments. These data suggest that an antigen-immune (Fab) complex may contribute to cholesterol cry stal function.