Method for producing heterologous bi-specific antibodies

A method for making heterologous bi-specific antibodies comprising the steps of:

• a) providing a quadroma fused from hybridomas of which one produces first antibodies which have an affinity to the binding domain of protein A wherein said first antibodies are mouse antibodies, human or humanized antibodies of the subclass IgG1, IgG2, IgG4 or rat antibodies of the subclass IgG2c and the other hybridoma produces second antibodies which, in comparison with the first antibodies, have a smaller or no affinity to the binding domain of protein A, the second antibodies being rat antibodies of the subclass IgG1, IgG2a, IgG2b, IgG3 or human or humanized antibodies of the subclass IgG3,
• b) multiplying and cultivating the quadromas in a culture,
• c) applying the quadroma culture supernatant to a column which is coated with a material having a grain size less than 50 .mu.m which contains binding domains of protein A as functional groups,
• d) washing out in the respective pH range the antibodies which are not bonded, and,
• e) subjecting the bi-specific antibodies to elution in a pH range of 5.6 to 6.0 which is at least 0.5 units above the pH at which the antibodies with greater affinity to the binding domain of protein A are still bonded.