FC-GAMMA-RECEPTOR ACTIVITY OF PLACENTAL ANNEXIN-II

We have previously produced a MoAb, B1D6, against a placental FcR. The antigen isolated using F(ab')(2)-fragments of B1D6 exhibits Fc-bindin g properties with low affinity for IgG. The antigen is a single-chaine d glycoprotein with a molecular weight of approximately 37 kDa and a p i of about 7.0-8.5. Amino acid sequences from enzymatic digests of the antigen indicated that it is annexin II. Immunoreactivity using anti- annexin antisera and purified placental annexin II have further establ ished the specificity of B1D6 to annexin II. The B1D6 epitope appears to be intramembraneous and intracellular on placental syncytiotrophobl asts, monocytes and other cells investigated.