text: Polyclonal antisera to either << b5R >> or cyt b5 significantly inhibited N-hydroxy-4-aminobiphenyl ([[ NHOH-4-ABP ]]) reduction by 95 and 89%, respectively, and immunoreactive cyt b5 protein content in individual HLM was significantly correlated with individual reduction of both NHOH-4-ABP and N-hydroxy-PhIP (NHOH-PhIP).