bio-World provides immobilized E. coli proteins on a solid bio-affinity support for the removal of antibodies to E. coliproteins from antisera prepared against recombinant proteins expressed in E. coli. Our immobilized E. coli lysate consists of partially purified proteins from E. coli strains commonly used for protein expression. The coupling chemistry is leak-resistant and provides a matrix with very low nonspecific binding. A column of immobilized E. coli lysate thus functions as a "reverse affinity matrix". The contaminating E. coli antibodies are absorbed onto the matrix and the purified antisera passes through for further use.