Sentence:  In the present work whole sera have been fractionated by chromatography on DEAE-cellulose using single gradients similar to those described by Sober and Peterson , and certain chemical and serological properties of the fractions containing <WSD>antibodies</WSD> of the ABO and Rh systems have been described . 
Meaning of the word marked with <WSD> tags:  any of a large variety of proteins normally present in the body or produced in response to an antigen which it neutralizes, thus producing an immune response