Sentence:  The third , containing the mixed type of complete and incomplete <WSD>antibodies</WSD> , had titers of 1 : 256 in saline , 1 : 512 in albumin and 1 : 1024 by the indirect Coombs test . 
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