CD w75 (LN1)

Biogenex (LN1), Dako (LN1), Immunotech (LN1), Novocastra, Sigma Chemical (LN1), Zymed (LN1).

LN1 is applicable to formalin-fixed, paraffin-embedded tissue sections. Enzyme or heat pretreatment before immunostaining improves immunodetection.

The CD w75 epitope is a sialylated carbohydrate determinant generated by theb-galactosyl a 2,6 sialyltransferase and has a molecular weight of 53 kD. Sialyltransferase catalyzes the incorporation of sialic acid to the carbohydrate group of glycoconjugates. Alterations on the cell surface of the oligosaccharide portion of glycoproteins and glycolipids are thought to play a role in tumorigenesis (Reed et al, 1993). Sialyltransferase has been found to be elevated in different tumor tissues and in serum of cancer patients. Further, the amount of sialic acid correlates with the invasiveness and metastasizing potential of several human tumors. Therefore the CD w75 epitope can be viewed as a target for identifying biologically aggressive tumors (David et al, 1993).
LN1 belongs to the CD w75 group of antibodies and recognizes a sialo antigen (45-85 kD). LN1 stains B lymphocytes in the germinal center with no reaction with T cells. It also reacts with a variety of epithelial cells including distal renal tubules, mammary glands, bronchus and prostate.

CDw 75 antigen expression has been examined in breast lesions (Reed et al, 1993). Duct carcinoma showed diffuse cytoplasmic staining in 21% of in situ and 35% of invasive carcinomas respectively. No correlation was demonstrated between immunoreactivity for CD w75 in breast carcinomas and their metastatic potential. However, CD w75 was more frequently expressed in high-grade carcinomas. A positive immunoreaction was demonstrated in benign proliferating lesions: intraductal papillomas (2/3) and epitheliosis in fibrocystic disease (10/14). This high frequency of immunoreactivity among the benign breast lesions was ascribed to activation of epithelial cells.
CD w75 epitope expression has also been examined in gastric carcinomas and their metastases (David et al, 1993). Forty-one cases (47%) were immunopositive for CD w75 antigen in the primary tumors or metastases. In contrast to breast carcinomas, a close relationship was found between antigen in primary tumors and their respective metastases. In addition, antigen expression correlated with an infiltrative growth pattern, lymphatic invasiveness and aneuploidy whilst no correlation was found with gastric carcinoma morphology, lymphoid infiltrate, vascular invasion and gastric wall penetration. Hence, CD w75 expression appears to be a good indicator of the biologic aggressiveness of gastric carcinoma.
LN1 is an excellent marker for B-cell lymphomas, especially follicular-derived lymphomas. In B cells, the LN1 antibody produces a typical membrane and cytoplasmic (paranuclear "dotlike" or Golgi) staining pattern. No immunoreaction is present with small lymphocytic lymphomas and T-cell lymphomas. LN1 also reacts with L&H cells in nodular lymphocyte-predominant Hodgkin's disease.

In view of the contrasting results between breast and gastric carcinoma, further studies examining CD w75 expression in these and other cancers are awaited. Follicular lymphomas or epitheliosis of the breast or gastric carcinoma are most suitable for use as positive control tissue.

•David L, Nesland JM, Funderud S, Sobrinho-Simoes M. 1993 CD w75 antigen expression in human gastric carcinoma and adjacent mucosa. Cancer; 72: 1522-1527.

•Reed W, Erikstein BK, Funderud S et al. 1993 CD w75 antigen expression in breast lesions. Pathology Research and Practice 189: 394-398.

Manual of diagnostic antibodies for immunohistology / Anthony S.-Y. Leong, Kumarasen Cooper, F. Joel W.-M. Leong.