Mouse monoclonal antibody raised against a partial recombinant PGR. This PGR gene uses two distinct promoters and translation start sites in the first exon to produce two isoforms, A and B. The two isoforms are identical except for the additional 165 amino acids found in the N-terminus of isoform B. Our immunogen corresponds to the specific region of isoform B, thus this antibody is a PGR isofrom B specific antibody.