Monoclonal antibodies against Galα 1 −4Galß 1 −4Glc(Pk, CD77) produced with a synthetic glycoconjugate as immunogen: Reactivity with carbohydrates, with fresh frozen human tissues and hematopoietic tumors

The purpose of this study was to isolate mouse monoclonal antibodies (MAbs) recognizing Galα I -4Galβ I −4Glc (Pk. CD77), which has been described as a Burkitt's-lym homa-associated using a synthetic glycoconjugate as immunogen and a filter immunoplaque screening assay. One MAb (PK67) was characterized by immuno-thin-layer chromatography, ELISA and competition assays using neutral glycolipids from various sources and a variety of carbohydrates and glycoproteins. Epitope analysis showed that all 3 carbohydrate moieties are required in PK67 binding. No cross-reactivity was observed with closely related carbohydrate structures, with the exception of Galα I -4Ga1β I -4GlcNAc. However, the reactivity with this structure was several orders of magnitude lower than with Pk. lmmunohistochemical analysis of fresh-frozen tissue specimens showed that Gb3, is widely expressed: prominent staining was observed in many normal tissues, e.g., kidney and gastric tissue and on capillary endothelial cells. In lymph nodes, very weak staining of a few B cells was observed. Flow cytometric analysis of hematopoietic neoplasms showed Gb, expression on B-cell neoplasms, particularly those with committed 8-cell phenotype indicating that, in addition to earlier reports of Gb3, expression on Burkitt's lymphoma, Gb3, is present on other committed B-cell neoplasms.