CA19-9, a carbohydrate epitope expressed on a high MW (>400 kDa) mucin glycoprotein, is a sialyl Lewisa structure which is synthesized from type 1 blood group precursor chains and is present in individuals expressing the Lewisa and/or Lewisb blood group antigens. In normal tissues, sialyl Lewisa antigen is present in ductal epithelium of the breast, kidney, salivary gland, and sweat glands. Its expression is greatly enhanced in serum as well as in the majority of tumor cells in gastrointestinal (GI) carcinomas, including adenocarcinomas of the stomach, intestine, and pancreas. Preoperative elevated CA19-9 levels in patients with stage I pancreatic carcinoma decrease to normal values following surgery. When used serially, CA19-9 can predict recurrence of disease prior to radiographic or clinical findings. This MAb is excellent for staining of formalin-fixed, paraffin-embedded tissues.Primary antibodies are available purified, or with a selection of fluorescent CF® Dyes and other labels. CF® Dyes offer exceptional brightness and photostability. Note: Conjugates of blue fluorescent dyes like CF®405S and CF®405M are not recommended for detecting low abundance targets, because blue dyes have lower fluorescence and can give higher non-specific background than other dye colors.