Interaction of immunoglobulins with liposomes.

Abstract

A B S T R A C T Liposomes were used as model targets to test the effect of immunoglobulins on biomembranes. Heat-aggregated immunoglobulins (Ig) exceeded native immunoglobulins in their capacity to release anions and glucose from model liposomes (either lecithin-dicetylphosphate-cholesterol or lecithin-stearylamine-cholesterol in molar ratios of 7: 2: 1). This interaction was not dependent upon the presence of cholesterol in the membrane. Mild heat-aggregation (10 min at 61.50C) increased the membrane-perturbing activity of certain 1g. Activity varied among classes and subclasses: IgG > pooled IgG > IgG4> IgA, > IgGs. IgG2, IgA2 and IgM were inert. Fc fragments of IgG were as active as IgGi, whereas Fab fragments were inactive. Prolonging aggregation to 60 min destroyed the activity of 1g. Membrane-activity could not be induced in non-Ig molecules (such as bovine serum albumin) by 10 or 60 min heat-aggregation. Density gradient centrifugation of IgG, molecules indicated that membrane perturbing activity was associated with 15-20-s aggregates. Sepharose 4B chromatography demonstrated preferential interaction between cationic membranes and aggregated Ig, whereas anionic membranes interacted nonselectively with both native and aggregated Ig via salt-like interactions. One explanation for these data is that heat aggregation induces a conformational change in the Fc regions of certain Ig permitting them to interact with liposomes, presumably by enhancing their hydrophobic associations with membrane phospholipids.

Complement and immunoglobulins stimulate superoxide production by human leukocytes independently of phagocytosis.

“…Serum-treated zymosan can bind to human PMN via "specific" receptors for the opsonic fragment of the third component of complement which coats these particles (14,15). The reactive site on aggregated IgG appears to reside on the Fc region which can engage and perturb lipid membranes (16). Aggregated IgG may also react with more specific receptors on the cell surface (17,18).…”

A general method for the introduction of enzymes, by means of immunoglobulin-coated liposomes, into lysosomes of deficient cells.

“…Since it is doubtful that the phospholipid surfaces of liposomes constitute a strong endocytic stimulus to the lysosomal system (11), we reasoned that cells might actively ingest enzyme-containing liposomes if these were coated with aggregated immunoglobulin (12,13). We have previously shown that leukocytes will endocytose immune precipitates in heat-inactivated serum (12), and that aggregated immunoglobulins preferentially associate with liposomes (13) (Pharmacia, Stockholm).…”

“…We have previously shown that leukocytes will endocytose immune precipitates in heat-inactivated serum (12), and that aggregated immunoglobulins preferentially associate with liposomes (13) (Pharmacia, Stockholm). Aliquots of liposomes (5 ml) were applied to 2.5 X 20-cm columns (operating pressure: 20 cm of water) with a flow rate of 0.1-0.5 ml/min; elution was in 0.145 M NaCl-KCl (equimolar) containing 0.05 M phosphate buffer (pH 7.4).…”

“…Aliquots of liposomes (5 ml) were applied to 2.5 X 20-cm columns (operating pressure: 20 cm of water) with a flow rate of 0.1-0.5 ml/min; elution was in 0.145 M NaCl-KCl (equimolar) containing 0.05 M phosphate buffer (pH 7.4). Column fractions (1-3 ml) were analyzed for peroxidase as described by Steinman and Cohn (16); they were analyzed for liposomes (apparent absorbance at 410 nm) and for glucose (glucose oxidase method) or CrO4= (absorbancy at 370 nm) as described (1,13,19). [Glucose] and [CrO4l were assayed in liposome-rich fractions after addition of 0.2% Triton X-100 (v/v).…”

The Impact of Protein Binding on Antibacterial Activities of Antibiotics is more than Predicted by Considering its Numerical Value Alone: Impact of Preparative and Incubation Methods on Different Pharmacodynamic Endpoints of ß-Lactams, Macrolides, or Fluoroquinolones Against Gram-positive and Gram-negative Bacteria-Part I

“…Changes in the pH of the test media have a significant effect on in vitro activities of macrolides, fluoroquinolones and aminoglycosides but leaving ß-lactams unaffected [25][26][27][28][29]. Furthermore, storage time and freeze-thaw cycles affect the stability of some serum proteins including albumin [30][31][32] and exposure of serum to heat as used for complement inactivation induced conformational changes of serum proteins affecting their interaction with bacterial membranes and antigens [33][34][35][36][37][38][39].…”