Monoclonal antibodies from mice bearing human colorectal carcinoma xenografts

We have examined the serological response in immunosuppressed mice bearing xenografts of the human colorectal carcinoma line HT29. The sera of such animals contain antibodies which bind to HT29 cell membrane components. This antibody activity was not completely absorbed by either human lymphocytes or red blood cells suggesting that at least part of this activity is directed against tumour-associated antigens. By fusing the spleens from tumour-bearing animals to an established myeloma line we were able to produce 34 monoclonal antibodies which bound to HT29 cells. The specificity of these antibodies in binding assays against membrane preparations from a variety of normal and malignant tissues and cell lines was determined. Twenty-seven bound to components present on both normal and malignant human cell membranes; 4 to tumour membranes only, whilst 3 bound specifically to membranes prepared from colorectal carcinoma tissue or cell lines. Thus despite immunosuppression the xenograft-bearing mouse was able to recognise a number of antigens present on the tumour surface.