Enhanced staining for Leu M1 (CD15) in Hodgkin's disease using a secondary antibody specific for immunoglobulin M

A practical approach for evaluating new antibodies in the clinical immunohistochemistry laboratory

Paraffin section immunohistochemistry (IHC) is widely used in diagnostic surgical pathology. Today, it is difficult to imagine the practice of surgical pathology without IHC. The availability of automated immunostainers with reagent rental contracts makes this technology commonplace. One potential danger is that many laboratories are now offering immunostains without significant prior knowledge or experience in IHC. As part of its mission, the Cell Markers Committee of the College of American Pathologists offers this manuscript as a basic guide to introducing new antibodies in the clinical IHC laboratory. Issues relating to regulatory developments, antibody selection, staining optimization, and test validation are addressed.

Differential reactivity of HBME-1 and CD15 antibodies in benign and malignant thyroid tumours. Preferential reactivity with malignant tumours

We studied a wide range thyroid tumours and non-neoplastic conditions (total 463 cases) immunohistochemically to evaluate the possible diagnostic potential of HBME-1 and CD15 antibodies. HBME-1 monoclonal antibody recognizes a biochemically unknown epitope present in mesothelioma and variably present in some adenocarcinomas. CD15 antibodies recognize a sugar epitope also included in Lewis X blood group antigen. All papillary (145/145) and follicular carcinomas (27/27) were HBME-1 positive, usually in the the majority of tumour cells. In contrast, cases of nodular goitre and papillary hyperplasia either showed no reactivity or were focally positive (in a third of cases). The patterns of CD15 reactivity were generally similar, although smaller numbers of tumour cells were positive in papillary carcinomas, and only 50% of follicular carcinomas were positive. Because fetal thyroid also showed CD15 reactivity, this antigen appears to behave as an oncofetal antigen in relation to thyroid tissue. Anaplastic carcinomas were negative with both antibodies, indicating the loss of these epitopes upon high grade malignant transformation. We conclude that HBME-1 and CD15 immunohistochemistry may be helpful in the histological differential diagnosis between benign lesions and differentiated thyroid carcinomas, especially papillary tumours. Although the biochemical basis of HBME-1 reactivity is unknown, increased CD15 reactivity in malignant thyroid tumours probably reflects changes in thyroid follicular epithelial glycoconjugates related to malignant transformation.

Comparison of the pattern of expression of Leu-M1 antigen in adenocarcinomas, neutrophils and Hodgkin's disease by immunoelectron microscopy

The mouse monoclonal antibody anti-Leu-M1 (CD15) recognizes the carbohydrate determinant lacto-N-fucopentaose III, an oligosaccharide believed to be involved in cell-cell interactions. Anti-Leu-M1 is used in surgical pathology as an aid in the diagnosis of Hodgkin's disease. Additionally, adenocarcinomas derived from various organs stained positively with anti-Leu-M1 at the light microscopic level. Since mesotheliomas do not display positive reactivity to this antibody, Leu-M1 is clinically useful as part of a panel of antibodies in distinguishing adenocarcinomas from mesotheliomas. Previous work was carried out using post-embedding protein A-gold immunocytochemistry on thin sections embedded in Lowicryl K4M from a patient with Hodgkin's disease of the nodular sclerosing type; intense and precise labeling by gold particles was revealed in cytoplasmic granules, which were often clustered in a perinuclear location, in the Golgi apparatus, and focally along the plasma membrane of Reed-Sternberg cells. Moreover, polymorphonuclear leukocytes demonstrated similar labelling along the plasma membrane and over cytoplasmic granules. To define precisely the intracellular localization of Leu-M1 in human adenocarcinomas, we have performed post-embedding immunoelectron microscopy with the protein A-gold technique on sections embedded in Lowicryl K4M from neoplasms of the lung, stomach, colon, and breast. The pattern of labeling by gold particles indicative of Leu-M1 binding varied in adenocarcinomas of the different organs.

Immunohistochemical analysis of Hodgkin's disease using microwave heating

AIMS

To assess the effect of microwave heating on immunohistochemical staining of CD15 and CD30 antigens in Hodgkin's disease tissue samples.

METHODS

Formalin fixed, paraffin wax embedded sections from 20 cases of Hodgkin's disease (six mixed cellularity, 14 nodular sclerosis) were immunostained for CD15, using two antibodies (DAKO-M1 and Leu-M1) and for CD30 using the antibody Ber-H2. The staining was carried out by conventional techniques which included pretreatment of sections with trypsin and on untreated sections following heating with microwaves. With antibody Leu-M1 an additional method, using a specific antimouse IgM bridge both with and without microwave heating, was also included. The results for each method were compared by counting positively stained Reed-Sternberg cells and estimating the staining intensity.

RESULTS

Microwave heating resulted in a substantial increase in the number of cells stained with antibodies to CD15 and also in the staining intensity. The best results were obtained using Leu-M1 with specific rabbit anti-mouse IgM bridge and microwave heating. Dramatic enhancement of the staining of Reed-Sternberg cells for CD30 was achieved following microwave heating, together with disappearance of the non-specific staining of plasma cells.

CONCLUSION

Microwave heating is strongly recommended for the immunohistochemical staining of CD15 and CD30 expressed by Reed-Sternberg cells in Hodgkin's disease.