Production and characterization of monoclonal antibodies against Panulirus interruptus hemocyanin

Influence of antibody binding on oxygen binding behavior of Panulirus interruptus hemocyanin

Oxygen binding behavior of monomeric subunit a and the hexameric form of this subunit of hemocyanin of Panulirus interruptus is influenced by the binding of various monoclonal antibodies. These antibodies react with other surface parts of the subunit than its second domain in which the oxygen binding site is located. The influence of three monoclonal antibodies and their antigen binding fragments (Fab) has been investigated. Two antibodies increase the oxygen affinity of monomeric hemocyanin from that observed in its low affinity T-state, while the third has little influence on this property. Fab fragments abolish almost completely the cooperativity of oxygen binding by the hexameric hemocyanin molecule. The two antibodies which increase the oxygen affinity of the monomeric molecule stabilize high-affinity states of the hexameric molecule, while the third stabilizes the low-affinity state.

Dimerization of an antigenic peptide leads to strong interaction with its antibody

A sequential epitope reacting with a monoclonal antibody against Panulirus interruptus hemocyanin was localized in the C-terminal CNBr peptide. As the antibody reacted with about equal affinity with different subunits of this and with hemocyanin from another spiny lobster, Palinurus vulgaris, the epitope was assigned to a conserved sequence region. The CNBr peptide, which was linked to another peptide via a disulfide bridge, was reduced and reoxidized. As a result, not the heterodimer but only the two disulfide-linked homodimers were formed. The dimeric C-terminal peptide had a much higher affinity for the monoclonal antibody than the monomeric peptide. This may be explained by the presence of two independent mobile interaction sites in each of the two reacting molecules.

Purification and characterization of a protein that permits early detection of lung cancer. Identification of heterogeneous nuclear ribonucleoprotein-A2/B1 as the antigen for monoclonal antibody 703D4

We have reported that a mouse monoclonal antibody 703D4, detects lung cancer 2 years earlier than routine chest x-ray or cytomorphology. We purified the 703D4 antigen to elucidate its role in early lung cancer biology, using Western blot detection after SDS-polyacrylamide gel electrophoresis. Purification steps included anion exchange chromatography, preparative isoelectric focusing, polymer-based C18-like, and analytical C4 reverse phase high performance liquid chromatography. After 25-50,000-fold purification, the principal immunostaining protein was > 95% pure by Coomassie staining. The NH2 terminus was blocked, so CNBr digestion was used to generate internal peptides. Three sequences, including one across a site of alternate exon splicing, all identified a single protein, heterogeneous nuclear ribonucleoprotein-A2 (hnRNP-A2). A minor co-purifying immunoreactive protein resolved at the final C4 high performance liquid chromatography step is the splice variant hnRNP-B1. Northern analysis of RNA from primary normal bronchial epithelial cells demonstrated a low level of hnRNP-A2/B1 expression, consistent with immunohistochemical staining of clinical samples, and increased hnRNP-A2/B1 expression was found in lung cancer cells. hnRNP-A2/B1 expression is under proliferation-dependent control in normal bronchial epithelial cell primary cultures, but not in SV40-transformed bronchial epithelial cells or tumor cell lines. With our clinical data, this information suggests that hnRNP-A2/B1 is an early marker of lung epithelial transformation and carcinogenesis.