Renée Norberg

Anti-actin antibodies.

Although antibodies against actin were claimed to have been experimentally produced by Kesztyus et al. (1949) and subsequently by several others (Marshall et al., 1959; Tunik and Holtzer, 1961; Pepe, 1966; Hirabayashi and Hayashi, 1972), the specificity of the antisera produced was nevertheless questioned (Bray, 1974). Actin, which is present in almost every cell of all animals, has even been considered nonantigenic because of its strongly conserved structure with very small differences between species. Thus, all animals should be tolerant, and this would explain the many unsuccessful attempts to produce antisera against actin.

Effects of cytochalasin B on fibroblasts, lymphoid cells, and platelets revealed by human anti-actin antibodies

Abstract Human antibodies against actin revealed on smeared lymphoblastoid cells a strong staining of numerous microvilli of different lengths extending from the cell surface. Smeared human platelets stained by anti-actin serum showed a bright cytoplasmic fluorescence and projections extending from the surface. Human fibroblasts spread on glass were multi-shaped, and anti-actin serum revealed brightly stained fibers running through the cells. After treatment with cytochalasin B, all types of cells investigated became rounded up, and surface projections could not be demonstrated. The staining pattern indicated a redistribution of the cellular contractile proteins after cytochalasin B treatment. Cytochalasin B did not impair the antigenicity of actin, since presence of the drug did not influence the antibody absorbing capacity of actin. Culture of lymphoblastoid cells and human fibroblasts in the presence of colchicin did not influence the staining pattern of actin antibodies.

Monoclonal antibodies to epitopes shared by actin and vimentin obtained by paramyxovirus immunization

Three hybridoma clones producing IgM antibodies against actin were obtained from mice immunized with purified virions of paramyxoviruses. When tested on growing lung fibroblasts, ascites fluids of all clones stained in immunofluorescence cytoplasmic bundles of microfilaments, but also fibrillar networks. On colchicine-treated cells, perinuclear coils were seen in addition to microfilament bundles. In addition, one clone gave a pronounced speckled staining to the nuclei. Absorption of the ascites fluids with purified actin abolished all staining patterns. Using the Western blotting technique the antibodies reacted with both actin and vimentin polypeptides. DNase I abolished the staining of the actin filaments and of the nuclei, but left the vimentin pattern unimpaired. Thus, the monoclonal antibodies evidently reacted with epitopes common to actin and vimentin.

Metabolism of Human Gamma Microglobulins

Birke, G., Norberg, R., Olhagen, B. & Plantin, L.-O. Metabolism of Human Gamma Macroglobulins. Scand. J. clin. Lab. Invest. 19, 171-180, 1967. The metabolism of gamma M-globulin was studied in 4 cases with macroglobulinaemia and 4 controls. The macroglobulinaemic cases received autologous preparations, one of them got his own cryoglobulin, two controls with severe cerebral lesions received gamma M-globulin prepared from macroglobulinaemic serum and 2 controls received gamma M-globulin from pooled normal sera.The fractional catabolic rate was independent of the serum gamma M-globulin level. It was found to be around 10 per cent, corresponding in the controls to 0.1-0.4 g per day and in macroglobulinaemia to 3.8-18.8 g per day.The macroglobulins remained predominantly in the intra-vascular compartment.Special attention was directed to the question of the metabolic behaviour of autologous and homologous gamma M-globulin. The metabolic data argued in favour of different initial treatment of homologous and aut...

Proteinuria in Patients with Urinary Tract Tumours

Serum and urine proteins were analysed by means of gel electrophoresis and immunoelectrophoresis in 12 patients with urinary tract tumours, 13 patients with glomerulonephritis, and 12 patients with pyelonephritis. Immunoglobulins (Ig A, Ig G, and Ig M) and transferrin were determined by means of immunological techniques. The clearance value of each protein or protein fraction was determined and expressed in relation to the albumin clearance. The tumour patients had a high excretion of immunoglobulins, especially Ig M, and a low excretion of alfa-1-globulin and transferrin compared with the other patients. The origin of proteinuria in patients with urinary tract tumours is discussed. In such patients the study of protein excretion may be of diagnostic value.

Ultrastructure of in vitro formed actin-anti-actin immune complexes

Abstract The reactions of five human smooth-muscle-antibody positive sera with F-actin from rabbit skeletal muscle were studied by electronmicroscopy with the negative contrasting technique. The immune complexes consisted of parallel arrays of actin filaments cross-linked by antibodies. Small complexes had a ladder-like appearance on some regions suggesting a periodic antibody binding. The antibodies were observed directly and by the aid of a ferritin-conjugated anti-human Ig.

Non-specific precipitin reactions of IgG at low ionic strength

Precipitin reactions apparently not involving specific antibodies were obtained in immunodiffusion experiments performed at low salt concentration between IgG and the muscle proteins, actin and tropomyosin. The precipitates, which dissolved at physiologic ionic strength, may result from electrostatic interaction of molecules of different net charge and different distribution and number of charged groups.