Production of anti-fibroblast growth factor receptor monoclonal antibodies by in vitro immunization

Monoclonal antibodies against the high affinity tyrosine kinase Fibroblast Growth Factor (FGF) receptor may help define receptor epitopes involved in FGF binding and signal transduction which mediate coronary and tumor angiogenesis (the development of blood vessels). Monoclonal antibodies against the FGF receptor were made by in vitro immunization. Receptor was PAGE-purified and transblotted to nitrocellulose. The nitrocellulose was dissolved with acetonitrile, and the receptor used as antigen in an in vitro immunization system. Screening for FGF receptor positive clones was done using membrane preparations from Coronary Venular Endothelial Cells (CVEC) expressing the FGF receptor, both by Enzyme Linked Immunosorbent Assay (ELISA) and Western blot. Culture supernatants of several clones tested positive for IgM or IgG monoclonal antibodies against the FGF receptor. Antibodies were affinity purified. Ascites fluid was produced in Balb/c mice primed with Incomplete Freund's adjuvant (IFA). The monoclonal antibodies were also found to be suitable for receptor immunoprecipitation. Immunocytochemistry was done on sections from a variety of species. Further characterization of these antibodies, as well as the production of the remainder of a panel of anti-FGF receptor monoclonal antibodies, is underway.

Evidence of high and low affinity binding sites for basic fibroblast growth factor in mouse placenta

The placenta has been shown to contain bFGF, but the presence of specific binding sites for this growth factor in this tissue remained to be established. In order to study the role of bFGF in the placenta growth, we looked for specific binding sites on mouse placental cell membranes at days 12, 14, 16, and 18 of pregnancy. At day 12, Scatchard analyses indicated that two classes of specific interaction sites for bFGF were detected. One class of high affinity binding sites was characterized by an apparent Kd of 10 pM and a binding capacity of 10 fmoles per mg of membrane protein. A second class of low affinity binding sites was detected with an apparent Kd of 60 nM and a binding capacity of 26 pmoles per mg of membrane protein. At days 14, 16 or 18, Scatchard analyses only showed low affinity binding sites with an apparent Kd of 24 nM and a binding capacity of 230 pmoles per mg of membrane protein. The characterization of these binding sites was performed by cross linking experiments that revealed two forms of specific complexes. This result suggested that the high affinity binding sites correspond to putative receptors with relative molecular masses equal to 65,000 and 85,000. The dramatic decrease of the high affinity receptor number after the 12th day of pregnancy, which is synchronous with the 9-fold increase of the low affinity binding site number, suggests that the biological activity of bFGF could be regulated by a balance between both the numbers of high and low affinity binding sites on placenta cell membranes. Thus, as it was shown for other growth factors, bFGF could only be involved at specific pregnancy stages.