Chromatographic study of the interrelationships of immunoglobulin A and alpha 1-microglobulin in myelomatosis

Electrophoretic, chromatographic and immunological studies of human urinary proteins

Urinary proteins from both sexes were analyzed by high resolution two-dimensional gel electrophoresis (2-DE). For well reproducible 2-DE patterns, the samples were concentrated and desalted in one step by vacuum dialysis. A reference map for urine proteins was established by the analysis of urine from 10 healthy persons. Proteins in urine that share immunogenicity with serum proteins were identified by use of antibody to whole human-serum protein in an affinity-column fractionation of urine and differential analysis of the adsorbed (serum component) and unadsorbed (non-serum component) fractions. For identification of individual proteins, coelectrophoresis, immunoblotting and affinity chromatography with corresponding antibodies were used. Proteins identified in the map, besides known serum proteins, included: the subunit of Tamm-Horsefall protein, the secretory component of IgA, constant breakdown products of alpha 1-antitrypsin and retinol-binding protein, the five isoforms of the beta chain of human chorionic gonadotropin and the subunit of prostatic acid phosphatase. In addition, we could demonstrate three proteins which are markedly pronounced in female urine, especially pregnant women. To get more information about the native properties of various urinary proteins, they were separated into four main peaks according to their sizes using fast protein liquid chromatography equipment. Possible interpolypeptide disulfide bonds were studied using a nonreducing 2-DE system. 2-DE in combination with other methods seems to be a valuable tool for the characterization of urinary proteins in defined renal or extra-renal diseases. An example is given by analyzing the immune complexes from seven patients with a urinary tract infection.

Human alpha 1-microglobulin: its measurement and clinical significance

alpha 1-Microglobulin (alpha 1-M), also called protein HC, is a low-molecular-weight (LMW) glycoprotein (about 30 kDa) with unique physicochemical properties. Using purified urinary alpha 1-M a standard and specific antibody against alpha 1-M, an assay system for alpha 1-M was developed, and the clinical significance of this protein was investigated by measuring total levels of alpha 1-M under physiological and pathological conditions. alpha 1-M is distributed in various body fluids: in serum, it consists mainly of free LMW alpha 1-M and monomeric IgA-alpha 1-M complex. The total alpha 1-M level in serum and urine usually reflects LMW alpha 1-M variation sensitively, and its determination is quite useful as an indicator of renal glomerulotubular dysfunction and hepatic dysfunction. Serum levels can vary, depending on IgA-alpha 1-M complex level, in parallel with the IgA concentration. The heterogeneity of alpha 1-M purified from different sources of urine by different procedures and underestimation of IgA-alpha 1-M complex by solid-phase antibody assays can be important causes for the discrepancy of serum levels between assays.

Chromatographic and electrophoretic studies of immune complexes in non-A, non-B hepatitis

Immune complexes isolated from two patients with chronic non-A, non-B hepatitis, one patient with acute non-A, non-B hepatitis and one patient with juvenile rheumatoid arthritis were examined by means of a combined chromatographic and electrophoretic method. Both analyses showed the presence of complexes consisting of IgG, IgM, complement c1q factor and albumin; no antigen constituents were detected. The IgG-to-IgM ratio varied from 1:1 to 4:1, suggesting that one could be dealing with complexes of both IgG-IgM and IgG-IgG types. Moreover, the detectable presence of c1q factor might indicate that such complexes were capable of activating complement.

Chromatography of complex protein mixtures

This review has shown that a variety of chromatographic techniques are available for fractionating proteins. Fortunately, high-quality columns of every type described in this review are commercially available. Most water-soluble proteins may be eluted from size-exclusion, hydrophobic-interaction, ion-exchange, metal chelate, and bioaffinity columns with ease. When this is the case, high recovery and retention of biological activity are the norm. The exception is reversed-phase chromatography where the organic solvents and acids used in polypeptide elution denature many proteins. When problems do occur, they are generally the result of unique structural features of the protein. Very hydrophobic proteins have presented the biggest problem in that they are difficult to solubilize, particularly with retention of biological activity. It has been found that zwitterionic and non-ionic detergents are the most suitable solubilizing agents, but urea has also been used in cases where hydrophobic interacts are not as strong. Unfortunately, there is still an element of trial-and-error in selecting the most suitable solubilizing agent. Heterogeneous glycosylation of proteins also presents a problem. Both neutral and charged monosaccharides can be incorporated into proteins through multiple steps at several sites. Thus, there is the potential in a sample for a large number of glycoprotein species which have the same polypeptide backbone and differing amounts of oligosaccharide. A problem arises when size-exclusion, ion-exchange, hydrophobic-interaction, reversed-phase and bioaffinity systems begin to discriminate between these very similar glycoprotein species. Chromatographic peaks can become very broad, due to incomplete fractionation, and the polypeptide chain of interest can be associated with multiple peaks. The separation of glycoproteins requires much more study before logical procedures can be suggested for column selection and operation. Aggregated species are another class of proteins which present occasional problems. Multimeric proteins are adsorbed to sorbents by a series of forces, among which are hydrogen bonding, hydrophobic interactions, and electrostatic forces. These forces are also responsible for the maintenance of quaternary structure in proteins. When the same forces dominate both retention of protein structure and adsorption at the sorbent surface, the quaternary structure of the protein can be disrupted during elution. Very basic proteins also present a problem in some cases. Columns with residual negative charges, such as a silica-based reversed-phase column, adsorb anionic species so strongly that they are difficult to elute.(ABSTRACT TRUNCATED AT 400 WORDS)

A double antibody radioimmunoassay for human alpha 1-microglobulin

Using purified alpha 1-microglobulin from urine and specific rabbit antiserum, a double antibody radioimmunoassay has been developed. The assay is sensitive to 3 ng/ml and covers a working range from 25-800 ng/ml. The recovery rates on the average were 91.8% in serum and 97.7% in urine. The coefficients of intra-assay variation ranged from 3.6-4.5% and those of inter-assay variation from 4.0-8.8%. Correlations in serum and urine between the present assay and single radial immunodiffusion (r = 0.972; r = 0.978) and enzyme-linked immunosorbent assay (r = 0.935; r = 0.971) were satisfactory.