A passive haemagglutination test for human anti-mouse antibody (HAMA) responses in patients undergoing immunoscintigraphy.

Sera from seven patients with ovarian or colorectal carcinoma who had been given only single injections of 131I or 111In labelled IgG1, IgG2a or IgG2b monoclonal antibodies for immunoscintigraphy 2 weeks to 9 months earlier were tested for their ability to agglutinate sheep red blood cells coated with a mouse monoclonal antibody. Six showed agglutination, and this was still seen when sera were diluted to 1/125 in four patients and as low as 1/3125 in the other two. Sera from rats and mice which had been injected with monoclonal antibody also caused agglutination, which in the case of the mouse sera is due to the presence of anti-idiotypic antibody. This study shows that it is feasible to detect HAMA by a rapid, simple, passive haemagglutination reaction.