the marked structural similarity of the m antigen and the a antigen , which is known to be a 1,2-linked homopolysaccharide of 4,6-dideoxy-4-formamido-alpha-d-mannopyranosyl units , accounts for cross-serological reactions of the two and the long-standing confusion surrounding the nature of their antigenic determinants .
C0003320
antigen
C0003316
antigenic determinants