Differences in the characteristics of human monoclonal and polyclonal anti‐D as revealed by immunochemical investigations: human monoclonal antibodies share specificities with natural antibodies

Abstract
SUMMARY. To determine the basis of the tissue cross‐reactions shown by some human monoclonal anti‐Rh D antibodies, we have investigated the tissue reactivities of 48 further human monoclonal antibodies (mAb) against D and other Rh antigens, and compared them with those of normal and anti‐D sera and immunoglobulin preparations, and affinity‐purified polyclonal anti‐D antibodies. Although we were unable to detect any tissue reactivities associated with the D‐binding fraction of polyclonal antisera or prophylactic immunoglobulin, the non‐erythroid cell types identified by the tissue‐reactive human anti‐Rh mAb of both IgM and IgG class were those recognized by antibodies present in both normal and anti‐D sera. These results indicate: (a) that the tissue specificities of human anti‐Rh mAb are similar to those of natural antibodies, and (b) that there are immunochemical differences between polyclonal and monoclonal anti‐D antibodies, at least of IgG class, which may be relevant to the use of the latter in the prevention of haemolytic disease of the new‐born by immune prophylaxis.