Structural Patterns in Anti-DNA Autoantibodies: A Molecular Modeling Study

Anti-DNA autoantibodies are the hallmark of the autoimmune disease systemic lupus erythematosus. Although these antibodies are both diagnostic and pathogenic, little is known about their structures and the manner in which they recognize DNA antigens. To address the first of these points we have predicted the three-dimensional structures of 40 monoclonal anti-DNA F(ab) fragments derived from lupus-prone mice. These antibodies were chosen to encompass several different autoimmune strains along with the known variable region gene families that encode anti-DNA. We find that the structures of the antigen binding regions of these antibodies fall into three main classes, irrespective of both the mouse strain and genetic origins of the antibody. Specifically, high-affinity anti-ssDNA appear to possess a narrow channel that is presumably used for ligand recognition, whereas the binding site on anti-dsDNA is an open surface that is large enough to accommodate a DNA duplex. These findings provide structural data to support the hypothesis that anti-DNA arise by DNA-driven B cell activation and clonal expansion.     

The chicken lacrimal gland, gland of Harder, caecal tonsil, and accessory spleens as sources of antibody-producing cells

Accessory spleens, the caecal tonsil, the lacrimal gland, and the gland of Harder of chickens were assayed for PFC following intravenous injections of SRBC. These organs were negative for PFC with the exception of the accessory spleens which approach the main spleen in PFC frequency. In contrast, topical inoculation of the eye orbit by dropping SRBC onto the eyeball did stimulate the production of PFC in the Harderian gland as well as in the spleen.     

Membranes of animal cells. I. Methods of isolation of the surface membrane

Procedures have been devised for the isolation of the surface membranes of mouse fibroblasts (L cell) and a variety of other cells. The surface membranes are stabilized by various reagents in a hypotonic solution and are then removed intact or as large fragments with a Dounce homogenizer. The membranes are purified by differential centrifugation on solutions of sucrose or glycerol or on a column of fine glass beads. A trilaminar pattern can be seen in thin sections of the membrane in the electron microscope. Sufficient material can be conveniently obtained for chemical analyses.     

Effects of growth phase and boiling of enteropathogenic Escherichia coli strains on their interaction with Pseudomonas aeruginosa lectins

Escherichia coli strains from' serotypes O86, 0128 and O111 varied in their reactivity with Pseudomonas aeruginose lectins (PA-I with D-galactose specificity and PA-II which binds L-fucose, D-mannose, L-galactose and D-fructose). Generally, cells of O86 strains were agglutinated by PA-I, but not by PA-II, and those of O128 serotype were agglutinated by PA-II, and not by PA-I. Adsorption tests showed that cells of E. coli O86 strains adsorb PA-I to a greater extent than PA-II, while most E. coli O128 strains adsorbed higher amounts of PA-II. Cells of E. coli O111B4 which were not agglutinated by either Pseudomonas lectin could still adsorb both. Boiling of O86 and O128 cells frequently enhanced their agglutinability as well as their lectin adsorption capacity. The agglutinability enhancement was somewhat more prominent in boiled stationary phase cells than in log phase cells probably due to late synthesis of the O antigen components concomitantly with the heat-sensitive components (K antigens) which masked them. PA-I agglutinating activity was inhibited by the lipopolysaccharide (LPS) extracted from E. coli O86 cells, while PA-II was inhibited by the LPS extracted from E. coli O128 cells. These findings indicate that the receptors to the Pseudomonas lectins probably reside in the terminal part of the O-specific-polysaccharide of the LPSs of these bacteria.