Multiple reactivity of monoclonal antibodies

The reactivity of 31 purified monoclonal antibodies (MAbs) with 10 unrelated protein antigens was determined by an enzyme-linked immunosorbent assay. Twenty-two of the monoclonal antibodies (71%) reacted with at least one of these nonhomologous antigens. Overall, there was positive reactivity in 27% of the tests. A larger incidence of multiple reactivities was observed with increasing concentration of the MAbs. Certain of these antibodies (29%) did not react with any nonhomologous tested antigens, whereas others had reactivity with multiple antigens. Multiple reactivity was observed with 6 of 14 of the hybridomas in a test that measured binding to a cell line. Multiple reactivity was more frequently observed when the MAbs were tested with complex antigens, such as keyhole limpet hemocyanin or a cell surface. These experiments demonstrate that MAbs frequently react with multiple antigens.