Abstract: Cells which produce antibodies which bind carbohydrate epitopes of glycoproteins are identified by screening with mucinous body fluids in raw, or preferably partially purified, form. Fine differences in antibody specificity may be detected by further screening with mucinous body fluids treated to alter the carbohydrate epitope interest, e.g., removal of sialic acid from a sialosyl Lewis-a epitope. The selected antibodies may be used in immunopurification, immunodiagnosis and immunotherapy.By this method, antibodies have been found whose binding to carbohydrate epitopes such as sialosyl Lewis-a is relatively insensitive to pH. Such antibodies are of particular value in immunological methods where pH is a consideration.