USE OF ANTI-(BETA-2 MICROGLOBULIN) MAB TO STUDY FORMATION OF AMYLOID FIBRILS

Three mAbs, IgG(1)k 1F11, 7B6 and 14H3, were raised against in vitro-s elf-aggregated beta 2-microglobulin. They recognize the native and unf olded forms of the protein and bind its fibrillar form that is present in amyloid tissue. When assayed in fibrillogenesis tests in vitro, mA b 14H3 inhibited fibril formation from beta 2-microglobulin. This mAb recognizes a sequential epitope corresponding to the C-terminal octape ptide, residues 92-99, of beta 2-microglobulin. By using synthetic pep tides it has been found that the integrity of the sequence is essentia l for the formation of the immunocomplex: the binding affinity is lowe red by one order of magnitude (K-d from 10(-7) M to 10(-6) M) by remov al of Met99 and completely abolished when both Asp98 and Met99 are los t or Arg98 is substituted with Lys. The other two mAbs, 1F11 and 7B6, which bind sequences 20-41 and 63-75, respectively, are without effect on beta 2-microglobulin fibrillogenesis. These two mAbs recognize bet a 2-microglobulin bound to the heavy chain in the major histocompatibi lity complex of type I located in the cell membrane, a property which is not shared by mAb 14H3.