A mouse monoclonal antibody against glycophorin A produced by in vitro stimulation with human red cell membranes

Polyreactivity of monoclonal antibodies made against human erythrocyte membranes with various pathogenic bacteria

Glycophorins comprise the major sialoglycoproteins of the human erythrocyte membrane. Several years ago we described a murine monoclonal antibody (MAb), designated 124,D-7 (IgM), developed by in vitro immunization with human erythrocyte membranes as antigen. We found the MAb reacted with a neuraminidase-dependent epitope on glycophorin A. Recent findings using ELISA with various bacteria as coating antigens have demonstrated strong cross-reactions of MAb 124,D-7 with some bacteria like Legionella and no reaction with bacteria such as Streptococcus pneumoniae. A second MAb, 130,E-4 (IgM), generated by the in vitro immunization technique, agglutinated human red cells irrespective of blood groups. This MAb showed strong cross-reactions with bacteria different from those being positive with MAb 124,D-7. The broad cross-reactivities of the two MAbs suggested that they are polyreactive antibodies. Sequencing of the V(H) and V(L) genes of MAb 124,D-7 showed germ-like sequences characteristic of polyreactive antibodies. The nucleotide sequences of the V(H) and V(L) genes of MAb 124,D-7 matched sequences coding for antibodies against CD34 and cross-reacting streptococcal antibodies. For Legionella pneumophila, the main interacting band on immunoblots was identified as the major outer membrane protein by mass spectrometry after separation by isoelectric focusing followed by SDS-PAGE. Flow cytometry showed that the epitope for MAb 124,D-7 was not displayed on live L. pneumophila but became exposed after heat treatment. Studies with one of the control MAbs, 145,F-2, directed against phosphorylcholine, which is known to be present on erythrocytes and some bacteria, showed that the epitope is deeply buried in the human erythrocyte membrane as neither neuraminidase nor papain exposed the epitope. The positive control MAb 3/1 directed against an epitope on LPS of L. pneumophila revealed weak cross-reactions with Pseudomonas aeruginosa.

Melanoma and the Problem of Malignancy

Of the overt biological properties exhibited by malignant cells two appear to command particular attention; these are (1) the transmigratory ability which empowers these cells to invade surrounding tissues and results in their metastatic and destructive potential, and (2) their ability to evade detection by the immune system of the host. Both of these characteristics may well involve several disparate mechanisms. However, it may be that there are some metabolic features that are common to malignant neoplasms which could go some way to explaining one of these behavioural anomalies. It is proposed that abnormalities of oxidative metabolism of cancer cells, resulting in the generation of reactive oxygen species, are responsible for the inhibition of the functions of vicinal antigen-presenting cells and, thus, the failure of the immune system to recognize tumour-specific antigens likely to be expressed by malignant cells as part of their transmigratory capability.

Shared epitopes of glycoprotein A and protein 4.1 defined by antibody NaM10-3C10

We have produced the murine monoclonal antibody (MAb) NaM70-3C10 (IgM) from splenocytes of mice immunized with human red blood cells (RBCs). The MAb agglutinated untreated as well as trypsin, chymotrypsin, neuraminidase, or ficin-treated RBCs from controls. In contrast, control RBCs treated with papaine or bromelaine were not agglutinated. On immunoblots, the MAb bound to glycophorin A (GPA) and to a 80 kDa protein identified as protein 4.1. Analysis by agglutination of variant RBCs carrying hybrid glycophorins made of the N-terminus (amino acids 1-58) of GPA and of the C-terminus (amino acids 27-72) of glycophorin B (GPB) and competition-inhibition test using purified GPA and a synthetic peptide corresponding to the amino acid sequence 48-58 of GPA demonstrated that the epitope is located within residues 48-58 of GPA. Epitope analysis with immobilized peptides showed that the MAb recognizes the sequence 53Pro-Pro-Glu-Glu-GIu58 of GPA. A homologous sequence is also present within amino acids 395 to 405 of protein 4.1. Finally, the MAb bound to 16 kDa chymotryptic peptide of protein 4.1, which carries the above amino acid sequence. In conclusion, it may be assumed that NaM70-3C10 specifically recognizes a common epitope on the extracellular domain of GPA and on the intracellular protein 4.1; this specificity explains the persistence of the 80 kDa band on blots when RBCs are treated with papain.

Fine characterization of a series of new monoclonal antibodies directed against glycophorin A

OBJECTIVES

Glycophorins A (GPA) and B (GPB) are the major sialoglycoproteins of the human erythrocyte (RBC) membrane. To prepare tools for the analysis of GPA and GPB, we produced a series of new monoclonal antibodies (mAbs) that identified epitopes of GPA.

METHODS

Seven murine monoclonal antibodies directed to glycophorin A (GPA) were fully characterized by agglutination of untreated and enzyme-treated human erythrocytes, inhibition of agglutination using chemically modified glycophorins and peptides from GPA, immunoblotting, and binding to synthetic peptides on plastic pins.

RESULTS

The antibodies identify epitopes located on four different portions of GPA. (1) NaM13-6D2 binds to the N-terminal portion of GPA and GPB carrying the N blood group antigen; (2) NaM26-3F4 recognizes the homologous portion of GPA and GPB corresponding to their amino acids 6-26; (3) NaM10-2H12, NaM16-IB10 and NaM10-6G4 are specific for the amino acid sequence 38-45 of GPA; and (4) NaM37-5F4 and NaM13-4E4 bind to the amino acid residues 119-124 located on the intracellular ponion of GPA.

CONCLUSION

These antibodies represent precise tools to investigate GPA and related molecules in different cells and tissues.

Generating monoclonal antibodies to neuronal antigens

Methods for generating monoclonal antibodies directed to the functional sites of neuronal antigens are reviewed. These methods include optimal antigen preparation and presentation as well as selective targeting and manipulation of the antigenic response. We describe our use of the immunosuppressant drug, cyclophosphamide, to produce a selective immune response to rare, poorly immunogenic, or actively suppressed antigens. These techniques allow us to generate antibodies to the functional sites of neuronal antigens, such as cell surface molecules. Such antibodies are directed to complex carbohydrates, proteins, protein complexes and glycolipids that form the active site of neuronal antigens. We can use these antibodies in the molecular dissection of functional active sites that are inaccessible to genetic manipulation. These techniques favor the generation of antibodies that can be used to understand and manipulate neuronal cellular activity.