sepharose and Lymphoma--B-Cell

The use of monoclonal antibodies (MAbs) in cytotoxic conjugates (radionuclides, toxins, or drugs) for targeting tumor cells is restricted due to toxicity in vital organs. Through improved tumor targeting, it is possible to administer larger amounts of such labeled MAbs, thus improving the ability to eradicate tumor cells without increased normal organ toxicity. Extracorporeal affinity adsorption treatment (ECAT) has therefore been developed using an avidin-agarose (AA) adsorbent with high binding affinity for the biotinylated radiolabeled MAb, rituximab. During ECAT, excess radioimmunoconjugates, not bound to the tumor cells, can be removed improving tumor targeting. The present study was performed to estimate the biocompatibility of the AA adsorber. Seven patients with B-cell lymphoma not responding to conventional treatment were studied. During the ECAT procedure, blood (B) components, plasma (P) complement fragments C3a, C5a, and P-bradykinin were analyzed, and other laboratory tests were carried out. Slight decreases in B-hemoglobin (8.3%), B-thrombocytes (11.4%), and P-albumin (14.3%) were observed, and could be explained by the dilution of the blood with normal saline and acid citrate dextrose. The AA adsorbent had no effect on the blood cells, immunological status or P-bradykinin level. The AA adsorber demonstrated good hemocompatibility and biocompatibility, without any side effects in the patients.

Topics: Adsorption; Adult; Aged; Antibodies, Monoclonal; Avidin; Extracorporeal Circulation; Female; Hemoperfusion; Humans; Lymphoma, B-Cell; Male; Materials Testing; Middle Aged; Radioimmunotherapy; Radioisotopes; Salvage Therapy; Sepharose

Epstein-Barr virus (EBV)-transformed human B-cell lines, L-KT9 and DH3 cells express CD23 antigen, and grow in a mixture of single and aggregated cells. The CD23 molecule has high amino acid sequence homology with C-type lectin and recently we have shown that the solubilized CD23 molecule can really interact with galactose residues on glycoproteins. In this study, therefore, we tested whether CD23 antigen on the cell surface really acts as a galactose-binding lectin in the aggregation of these cells. The EBV-transformed cells (L-KT9) were separated into an aggregated-cell-rich fraction and a single-cell-rich fraction. Aggregated cells disaggregated after removal of galactose by beta-galactosidase treatment, whereas single cells made large aggregation on sialidase treatment, and this aggregation was inhibited in the presence of asialo-fetuin. On the other hand, naturally aggregated cells become single cells with anti-CD23 monoclonal antibody (mAB) as well as the soluble form of CD23, but not with anti-CD21 mAB. In addition, L-KT9 and DH3 cells bound to asialo-fetuin-coupled Sepharose (ASF-Sepharose) and this binding was significantly inhibited by pre-treatment of cells with anti-CD23, but not with anti-CD21 or other anti-adhesion molecules. From these results, we conclude that the naturally aggregated state of EBV-transformed cells occurs mainly through the interaction of CD23 as a lectin molecule and galactose residues as its ligand.

Topics: alpha-Fetoproteins; Antibodies, Monoclonal; Asialoglycoproteins; B-Lymphocytes; beta-Galactosidase; Cell Aggregation; Cell Line, Transformed; Fetuins; Flow Cytometry; Galactose; Glycoproteins; Herpesvirus 4, Human; Humans; Lymphoma, B-Cell; Neuraminidase; Receptors, IgE; Sepharose; Tumor Cells, Cultured