Decreased suppressive B cell factor (SBF) in rheumatoid arthritis: evidence for a defect in B cell autoregulation

Rheumatoid arthritis (RA) is a disorder characterized by defective immunoregulation. Hypergammaglobulinemia, circulating immune complexes (IC), and autoantibodies such as rheumatoid factor (RF) are common serum abnormalities. To assess IC-mediated feedback suppression in RA, we evaluated the ability of a suppressive B cell factor (SBF) generated by culturing heat-aggregated IgG (HAIgG) with peripheral blood mononuclear leukocytes (PBL) from patients with RA and normal controls to suppress the pokeweed mitogen (PWM)-induced RF plaque-forming cell (PFC) response of normal PBL. RA patients generated less SBF than age-matched controls. Background suppression (supernatants obtained from PBL cultured without HAIgG) was similar in the RA patients and age-matched controls. To determine the effects of nonsteroidal antiinflammatory drug (NSAID) therapy on suppression, RA patients and age-matched controls were studied before and after NSAID therapy. NSAID therapy significantly reduced background suppression in RA patients who were not on immunosuppressive drugs and in age-matched controls, but there was no effect on SBF in RA patients or controls. There was a small increase in background suppression when NSAID were administered to RA patients on immunosuppressives, suggesting an ameliorative effect of NSAID in this group of patients, which tended to increase their level of suppression when compared with RA patients only on NSAID. Spontaneous RF-PFC were measured in normal controls and RA patients and were compared with suppressor activity. There were increased numbers of spontaneous RF-PFC in RA patients. Total suppressor activity was greatest in young adult controls, who also had the least RF-PFC. The percentage of suppression correlated inversely with the number of RF-PFC in patients and controls. Additionally, disease activity in RA as measured by total joint count and erythrocyte sedimentation rate (ESR) was shown to correlate inversely with total suppressor activity. We conclude that the PBL from patients with RA produce decreased SBF after HAIgG stimulation and that loss of suppression is also associated with aging. This study suggests a defect in IC-stimulated B cell suppressor activity in RA leading to decreased ability to suppress antibody and further IC formation. The combination of increased RF-PFC and decreased SBF suggests that there is defective B cell autoregulation in RA, which may be involved in the pathogenesis and chronicity of this disease.     

High purity preparations of higher plant vacuolar H+-ATPase reveal additional subunits. Revised subunit composition

A fast protein liquid chromatography procedure for purification of the V-type H+-ATPase from higher plant vacuolar membrane to yield near-homogeneous enzyme with a specific activity of 20-25 mumol/mg.min is described. When precautions are taken to ensure the quantitative recovery of protein before sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the preparation is found to be constituted of seven major polypeptides of 100, 67, 55, 52, 44, 32, and 16 kDa, respectively, and two minor components of 42 and 29 kDa. The 52-, 44-, and 32-kDa polypeptides do not cross-react with antisera raised to the 67- and 55-kDa subunits of the enzyme, and two independent sample preparation procedures yield the same apparent subunit composition. The additional polypeptides are not breakdown products or aggregates of the previously identified subunits of the ATPase. The ATPase of tonoplast vesicles is subject to MgATP-dependent cold inactivation, and the conditions for inactivation are identical to those for the bovine chromaffin granule H+-ATPase (Moriyama, Y., and Nelson, N. (1989) J. Biol. Chem. 264, 3577-3582). Cold inactivation is accompanied by the detachment of five major polypeptides of 67, 55, 52, 44, and 32 kDa from the membrane, and all five components co-migrate with the corresponding polypeptides of the purified ATPase upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The 100- and 16-kDa polypeptides of the ATPase are not removed from the membrane during cold inactivation, but the latter can be purified to homogeneity by chloroform:methanol extraction of the fast protein liquid chromatography-purified enzyme. It is concluded that the tonoplast H+-ATPase is constituted of 6-7 major polypeptides organized into a peripheral sector comprising the 67-, 55-, 52-, 44-, and 32-kDa components and an integral sector consisting of the 100- and 16-kDa polypeptides. The V-type H+-ATPase from animal endomembranes and higher plant vacuolar membranes therefore have remarkably similar subunit compositions and gross topographies.     

Cooling rates of living and killed chicken and quail eggs in air and in helium-oxygen gas mixture

1. In a helium atmosphere, heat is dissipated from a surface 3.5 times faster than it is in air. Eggs in a helium-oxygen atmosphere cool only 1.4 times faster than they cool in air. This signifies that internal resistance to heat flow is a significant factor in the cooling rates of eggs. 2. Heat flow occurs inside an egg in two ways: by conduction through the tissues and in flowing blood. Killing an embryo stops the latter, but not the former. Eggs cool more slowly after they have been killed, signifying that blood flow can be an important component in an egg's internal flows of heat. 3. Blood flow should be a relatively more important component of heat flow in large eggs than in small eggs. The difference in conductance between living and killed eggs is larger in 60 g chicken eggs than it is in 10 g quail eggs.     

Nearest-neighbor parameters for G.U mismatches: [formula; see text] is destabilizing in the contexts [formula; see text] and [formula; see text] but stabilizing in [formula; see text].

Thermodynamic parameters derived from optical melting studies are reported for duplex formation by a series of oligoribonucleotides containing G.U mismatches. The results are used to determine nearest-neighbor parameters for helix propagation by G.U mismatches. Surprisingly, the [formula; see text] nearest-neighbor free energy increment in unfavorable in the contexts [formula; see text], and [formula; see text] but favorable in the context [formula; see text]. This is a non-nearest-neighbor effect. In contrast, the [formula; see text] free energy increment is favorable and independent of context. Circular dichroism and imino proton NMR spectra of several sequences do not reveal an obvious structural basis for this dichotomy. For example, all the G.U mismatches have two slowly exchanging imino protons. The imino resonances for the G.U mismatches in GGAGUUCC, GUCGUGAC, and CCUGUAGG, however, broaden at lower temperature than the imino resonances for the interior Watson-Crick base pairs. In contrast, the imino resonances for the G.U mismatches in GGAUGUCC remain sharp at high temperature. The improved parameters for G.U mismatches should improve predictions of RNA structure from sequence.