Glucuronidation of 4′-OH DCF using UDPGA with rat liver microsomes (top) and bovine glucuronyl transferases (bottom). In each system, two products were formed (B and C) from starting material (A) over a 90-minute interval (insets). Product B was synthesized preferentially by rat liver microsomes, and product C by bovine glucuronyl transferases. The HPLC elution profile of substances B and C (90-minute samples) is shown in the larger graphs, and the ability of each substance to promote agglutination of normal RBCs by antibody from our patient is indicated above the respective peaks. Only material isolated from peak B was active in the agglutination assay.