Cross-reacting monoclonal anti-alpha 1-microglobulin antibodies produced by multi-species immunization and using protein G for the screening assay.

In order to generate monoclonal antibodies (MAb) directed against the low molecular weight glycoprotein alpha 1-microglobulin, a BALB/c mouse was immunized with a mixture of human, guinea pig, rat and rabbit alpha 1-microglobulin homologues (multi-species immunization) and boosted several times. On day 194, the mouse splenocytes were fused to SP2/0 myeloma cells. The resulting hybridomas were screened for anti-alpha 1-microglobulin activity against the alpha 1-microglobulin mixture or against the individual homologues. For this screening, protein G (the newly described IgG-binding streptococcal protein) was used in a solid-phase radioimmunoassay. The binding of protein G to immobilized antigen-antibody complexes was enhanced by pre-incubation with rabbit anti-mouse immunoglobulin G. The result was a panel of nine established hybridoma lines, all producing unique monoclonal antibodies, of IgG1 or IgG2a class, to alpha 1-microglobulin. The antibodies were not only reactive in solid-phase radioimmunoassay, but they could also immunoprecipitate 125I-labeled soluble alpha 1-microglobulin. Moreover, they reacted specifically with the alpha 1-microglobulin band in Western blots of urinary proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Such monoclonal antibodies are potentially valuable reagents for the further characterization of alpha 1-microglobulin.