Homogeneous endo-polygalacturonase (PG) was covalently bound to cyanogen-bromide-activated Sepharose, and the resulting PG-Sepharose conjugate was utilized to purify, by affinity chromatography, a protein from Phaseolus vulgaris hypocotyls that binds to and inhibits PG. Isoelectric focusing of the purified PG-inhibiting protein (PGIP) showed a major protein band that coincided with PG-inhibiting activity. PGIP formed a complex with PG at pH 5.0 and at low salt concentrations. The complex dissociated in 0.5 M Na-acetate and pH values lower than 4.5 or higher than 6.0. Formation of the PG-PGIP complex resulted in complete inhibition of PG activity. PG activity was restored upon dissociation of the complex. The protein exhibited inhibitory activity toward PGs from Colktotrichum lindemuthianum, Fusarium moniliforme and Aspergillus niger. The possible role of PGIP in regulating the activity of fungal PG's and their ability to elicit plant defense reactions are discussed.

We report on the occurrence of monoclonal components observed in a provincial hospital in northern Italy from 1987 to 1990. The monoclonal components were detected by visual inspection of high‐resolution acetate serum electrophoreses and typed by immunofixation. The percentage of monoclonal components increases steeply with age, and reaches a plateau of 7–8% in individuals over 55 years old. Besides the high percentage of monoclonal component, the other relevant finding of this study is that ˜80% of monoclonal components are of low concentration (<5 g/l). Most of these subjects with small monoclonal component passed undetected in the previous studies on the prognostic significance of monoclonal gammapathy. These findings indicate the need for a revision of the current concepts on the biological and clinical significance of MC discovered by chance.

SUMMARY. The study of proteinuria, and especially the search for Bence Jones proteins (BlP), has almost always required urine concentration. We evaluated a highsensitivity electrophoretic method using unconcentrated urine based on colloidal gold staining. The sensitivity for the detection of BlP is further enhanced by immunofixation, Sensitivity to HlP is better than 1 mg/L and, apart from the o-I microglobulin, all the proteins relevant to the classification of proteinuria can be visualized with a sensitivity of approximatively 3 mg/L.

The detection of Bence Jones protein, an important part of the investigation of suspected myeloma, is most commonly done by agarose or cellulose nitrate electrophoresis followed by immunofixation. Bence Jones protein is recognized as single or multiple bands of one type of light chain. Unfortunately, improvements in sensitivity of these techniques (use of high-affinity antisera and higher resolution electrophoresis) frequently allow detection of multiple light chain bands in the urine of patients who do not have a B-cell dyscrasia. The bands are usually kappa, although they may be accompanied by lambda bands. This pattern may lead to the misdiagnosis of Bence Jones protein and oligoclonal light chain production in patients. Here we show that this pattern is produced by polyclonal light chains; it is present in the urine of all patients with a tubular proteinuria of any etiology and may be induced in healthy individuals by blocking their renal tubular protein reabsorption. Polyclonal light chains separate into monomers and dimers on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and into four major bands with many minor bands by isoelectric focusing. This difference in charge and possibly size results in the banding pattern seen on good-quality electrophoresis and immunofixation.

We analyzed 708 serum samples from healthy children and adolescents by immunonephelometry to obtain reference values for the immunoglobulin kappa (kappa) and lambda (lambda) light chains and for their ratio at a time of life when immunoglobulin synthesis is maturing and continually being stimulated. The lambda chain concentration that is to be maintained throughout the child's life is reached very early, just after 1 year, whereas the concentration of the kappa chains, which increases gradually, reflects the concentration of the immunoglobulins as a whole. These reference values may be useful for studying kappa and lambda chains in illnesses involving the immune system in children.