Enzyme-linked immunoassay to monitor the purification of, and to screen for monoclonal antibodies against, C3b receptor.

An enzyme-linked immunosorbent assay both to screen for monoclonal anti-bodies to the C3b receptor and to monitor its purification was developed. The test requires only purified C3, converted to either the hemolytically no longer active iC3 or C3b. An NP-40 lysate of tonsil cells can be used as a source of CR1 in this test which works best under hypotonic conditions facilitating the interaction of iC3/C3b and CR1. Two monoclonal antibodies to CR1 were produced using this test for the screening of hybridomas. The identity of the molecule recognized by these antibodies with CR1 is demonstrated by immunoprecipitation and Western blot studies, as well as immunofluorescence and immunoperoxidase staining of cells and tissues known to contain CR1. Fractions from lentil-lectin and DEAE-Sephadex columns containing CR1 can be identified using this test.