Carbohydrate structure of sialyl 6-sulfo Le^x and nonsulfated sialyl Le^x and specificity of antibodies as ascertained by ELISA. The specificity of antibodies directed to sialyl 6-sulfo Le^x (G152), CLA (HECA-452), variant sialyl Le^x (2F3), and conventional sialyl Le^x (CSLEX-1) was ascertained by ELISA using pure synthetic carbohydrate determinants.