Theory and methods for immunization in culture and monoclonal antibody production

Is renin a factor in the etiology of essential hypertension?

The widespread clinical study of converting-enzyme inhibitors has shown that they are effective antihypertensive drugs even in patients who may manifest either normal or decreased plasma renin activity. This suggests either that renin in a site other than plasma may play a contributory role in essential hypertension or that the hypotensive effect is caused by increased concentrations of kinins and prostaglandins, both demonstrated consequences of converting-enzyme inhibitor administration. Specific renin inhibitors appropriate for studies in humans would aid in the resolution of this question. Four classes of compounds have been demonstrated to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogs of angiotensinogens, and peptides that are related to the amino-terminal sequence of prorenin. With the purification of renin, specific polyclonal or monoclonal antibodies have become available. The former have already been used extensively in physiologic studies in intact animals. Pepstatin is an inhibitor of many acid proteases. Its in vivo application has been retarded by its relative insolubility, but recent chemical modifications, particularly the addition of charged amino acids at the carboxy terminus, have rendered it more useful. The minimal substrate for renin is an octapeptide segment of the protein substrate: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have resulted in competitive inhibitors that are useful in vivo. Recently, remarkably active inhibitors have been synthesized by reducing the peptide bond that is cleaved by renin, producing what may be a transition state inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

An improved procedure for the 'dot immunobinding' analysis of hybridoma supernatants

The recently introduced dot immunobinding assay is well suited as a rapid and sensitive procedure for the analysis of those hybridoma clones that are producers of a specific antibody. We present a modification of the dot immunobinding assay which utilizes a single nitrocellulose sheet for up to 96 assays. By using a single nitrocellulose sheet, sample manipulation is greatly reduced, reaction conditions can be better standardized and a comparison of background reactivities is provided. Results are presented which demonstrate the effectiveness of this modified dot immunobinding assay.

Production of monoclonal antibodies against calmodulin by in vitro immunization of spleen cells

Monoclonal antibodies against the highly conserved ubiquitous calcium-binding protein, calmodulin (CaM), were produced by immunization of mouse primary spleen cell cultures. Dissociated spleen cells were cultured for 5 d in the presence of mixed thymocyte culture conditioned media (TCM) and purified bovine testes CaM (50 ng-1 mg). Following immunization, cells were fused with mouse myeloma cells (SP2/0, Ag 8.653) and cultured for 2-3 wk before initial screening for antibody. In five independent immunizations there was a range of 25-44% of the initial polyclonal cultures which produced antibodies reacting with purified CaM as determined by immunoassay. 80% of the cloned hybridoma produced IgM immunoglobulins while the remaining clones were IgG producers. This ratio was changed to 50% IgM and 50% IgG by subsequent extension of the in vitro immunization periods and reduced amounts of antigen and extended in vitro culturing. In vitro immunization introduces a new dimension to monoclonal antibody production where limited antigen or poorly antigenic proteins are of interest. The monoclonal antibodies produced in this study have enabled us to to selectively localize CaM in association with distinct subcellular structures, mitochondria, stress fibers, centrioles, and the mitotic spindle.

Inhibitors of renin: present and future

Four classes of compounds have been demonstrated to be renin inhibitors of high potency: specific antibody, general peptide inhibitors of acid proteases, analogs of angiotensinogen and peptides that are related to the amino-terminal sequence of renin's precursor (Pro-renin). With the purification of renin, specific polyclonal or monoclonal antibodies have become available. The former have already been used extensively in physiologic studies in intact animals. Pepstatin is an inhibitor of many acid proteases. Its in vivo application has been retarded by its relative insolubility, but recent chemical modifications, particularly the addition of charged amino acids at the carboxy-terminus have rendered it more useful. The minimal substrate for renin is an octapeptide segment of the protein substrate: His-Pro-Phe-His-Leu-Leu-Val-Tyr. Variants of this sequence have resulted in competitive inhibitors that are useful in vivo. Recently, remarkably active inhibitors have been synthesized by reducing the peptide bond that is cleaved by renin, producing what may be a transition state inhibitor. Several of these peptides have been shown to be effective as in vivo inhibitors of the hypertensive effect of the enzyme. The development of inhibitors based on Pro-renin sequences are awaited with interest.