Flow cytometric analysis of sialyl Lewis A antigen on human cancer cells by using F(ab')(2 mu) fragments prepared from a mouse IgM monoclonal antibody

F(ab')(2) fragments, herein designated as F(ab')(2 mu) fragments, were prepared from a mouse IgM monoclonal antibody specific to sialyl Lewis A antigen. The fragments were applied to flow cytometry to analyze the antigen on human cancer cells. The binding of the fragments to the antigen-positive cells was stronger than that of the original IgM. The non-specific binding of the IgM antibody to the antigen-negative cells was much decreased by using the F(ab')(2 mu) fragments. These results indicate that the F(ab')(2 mu) fragments are more suitable than the original IgM monoclonal antibody in flow cytometric analysis.