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PubMed1976

Evidence of a novel role for monovalent cations in pyruvate kinase catalysis.

In the pyruvate kinase (EC 2.7.1.40) reaction, the complete enzyme-products complex consists of enzyme, pyruvate, ATP, a divalent cation, and a monovalent cation, usually K+. The dissociation of this complex can be slow permitting reversible enolization of pyruvate in this complex during the course of the forward reaction. High concentrations of each component in the enzyme-products complex inhibits the forward reaction, but only elevated concentrations of the monovalent cation decrease the net rate of product dissociation relative to that of pyruvate enolization. This result indicates that the monovalent cation can be the first component released from the enzyme-products complex and that the presence of an inhibiting monovalent cation concentration leads to re-formation of the complete complex, which is necessary for pyruvate enolization. The evidence suggests that the monovalent cation can bind and release with each turnover of the enzyme. While the data do not permit the conclusion that first release of monovalent cation is the exclusive pathway for dissociation of the enzyme-products complex, no other component once released can reassociate rapidly enough to form a complete complex during the forward reaction. Inhibition by these components must be attributed to the formation of abortive complexes.

Adenosine Triphosphate↗
PubMed2002

Nonselective cation channels in plants.

Nonselective cation channels are a diverse group of ion channels characterized by their low discrimination between many essential and toxic cations. They are ubiquitous in plant tissues and are active in the plasma membrane, tonoplast, and other endomembranes. Members of this group are likely to function in low-affinity nutrient uptake, in distribution of cations within and between cells, and as plant Ca2+ channels. They are gated by diverse mechanisms, which can include voltage, cyclic nucleotides, glutamate, reactive oxygen species, and stretch. These channels dominate tonoplast cation transport, and the selectivity and gating mechanisms of tonoplast nonselective cation channels are comprehensively reviewed here. This review presents the first classification of plant nonselective cation channels and the first full description of nonselective cation channel candidate sequences in the Arabidopsis genome.

Amino Acid Sequence↗
PubMed1995

Organic cation transport by rat liver lysosomes.

Hepatic organic cation transport has been characterized in rat liver plasma membrane vesicles, using the quaternary amine tetraethylammonium (TEA) as a model substrate. Sinusoidal TEA uptake is stimulated by an inside-negative membrane potential; TEA transport across the canalicular membrane is mediated by electroneutral organic cation-H+ exchange. Substrates for these transport processes include procainamide ethobromide (PAEB) and vecuronium, cationic drugs that undergo biliary excretion. Given the apparent absence of sinusoidal transport mechanisms able to generate high hepatocyte-to-blood organic cation concentration ratios, intracellular transport of organic cations may involve sequestration and concentration within acidified organelles. Therefore, the characteristics of TEA uptake were examined in isolated rat liver lysosomes that are acidified by a well-described H(+)-adenosinetriphosphatase (ATPase). Lysosomal uptake of [14C]TEA was a time- and ATP-dependent process, reaching steady state after 30-60 min. Steady-state [14C]TEA uptake was significantly reduced by omission of ATP and by addition of monensin, conditions that alter lysosomal pH and membrane potential gradients, and by the H(+)-ATPase inhibitors, N-ethylmaleimide and bafilomycin A. ATP-dependent lysosomal [14C]TEA uptake was significantly inhibited by PAEB, vecuronium, and other organic cationic substrates of canalicular TEA/H+ exchange. These findings demonstrate that rat liver lysosomes sequester certain organic cationic drugs, most likely via organic cation/H+ exchange driven by H(+)-ATPase. Canalicular organic cation/H+ exchange may reflect, in part, the exocytic insertion of this transporter from an intracellular compartment to this membrane domain.

Adenosine Triphosphate↗
PubMed1991

Comparative insights into the mechanisms of renal organic anion and cation secretion.

Comparative models have played a major role in defining the mechanisms that enable vertebrate proximal tubules to transport organic anions and cations from the peritubular interstitium to the urine. The unique advantages of these models and their contributions to our understanding of organic anion and cation transport mechanisms are summarized here. Recent studies of the organic anion transport system suggest that transport is coupled to metabolic energy via indirect coupling to the sodium gradient. Organic anions enter the cell across the basolateral membrane in exchange for alpha-ketoglutarate (alpha-KG), and the alpha-KG is returned to the interior via Na-alpha-KG cotransport. Indirect coupling to Na has been demonstrated in both isolated membranes and intact renal epithelial cells of species ranging from marine crustaceans to mammals. This mechanism was shown to drive not only cellular accumulation but also secretory transepithelial fluxes of organic anions. Luminal exit of secreted organic anions appears to be carrier mediated but is, at present, poorly understood, with mediated potential-driven efflux and anion exchange-driven efflux implicated in some species. As for organic anions, the renal clearance of some organic cations approaches the renal plasma flow. Although there is considerable variation in the handling of specific substrates between species, the basic properties of organic cation transport include carrier-mediated potential-driven uptake at the basolateral membrane, intracellular sequestration that reduces the free concentration of the cation, and luminal exit by organic cation-proton exchange. Reabsorptive transport is also observed for some organic cations, but its mechanisms and driving forces are not well understood.

Animals↗
PubMed1981

Renal tubule transport of organic cations.

Transcellular active tubular transport of organic cations occurs in the proximal renal tubule in the direction of excretion. These organic cations may be primary, secondary, tertiary, or quaternary amines. Endogenous neurohumors such as choline and catecholamines and drugs such as morphine and tetraethylammonium are representative transportable organic cations. Competitive inhibition for transport is found among organic cations. Organic anions, however, do not compete for this transport. Organic cations used as drugs may interact with the transport of endogenous organic cations to alter the excretion patterns of both. Bidirectional active tubule transport can be demonstrated for choline and is accompanied by simultaneous renal metabolism of choline. Studies using vesicles prepared from luminal and antiluminal membranes of renal cortex suggest that organic cation transport occurs in both vesicle preparations. However, only the luminal vesicles showed the characteristics of carrier-mediated uphill transport.

Animals↗
PubMed1994

Role of cationic proteins in the airway. Hyperresponsiveness due to airway inflammation.

Major basic protein (MBP) is a highly cationic protein found in the granules of eosinophils. It has been postulated that MBP may participate in the pathogenesis of airway hyperresponsiveness exhibited by asthmatic patients. Accordingly, we have employed a rat system to investigate the effect of human MBP instillation on airway responsiveness and the possible role of cationic charge in the determination of this effect. Major basic protein caused a significant increase in airway responsiveness to inhaled methacholine. Two polycations, poly-L-arginine and poly-L-lysine, also increased airway responsiveness to inhaled methacholine. Moreover, two other very different cationic proteins, platelet factor 4 (PF4) and cathepsin G were also capable of inducing airway hyperresponsiveness. These effects were dependent on their positive charge, since the charge--and, hence the effect--of these proteins was neutralized with low molecular weight heparin. In addition, other polyanions, such as low molecular weight heparin, albumin, or dextran sulfate, were also effective. We investigated whether two synthetic cationic proteins, poly-L-arginine and poly-L-lysine, could modify epithelial-dependent responses using a perfused guinea pig tracheal tube preparation. With an intact epithelium, methacholine was some 150 times less potent when applied intraluminally than when applied extraluminally. Perfusion of the luminal surface with cationic proteins increased the potency of intraluminally applied methacholine without modifying the responses to extraluminally applied methacholine. Cationic proteins also attenuated the relaxant effects of intraluminally applied KCl. These effects occurred in the absence of any overt epithelial cell damage. Our data demonstrates that cationic proteins can modify epithelial-dependent responses in the airways.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Response of L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells to various metal cations.

Recent data suggest that under certain conditions, various metal cations are released from dental alloys. These ions may produce adverse effects in various cell types in vivo. In this study, the cytopathogenic effects of 13 metal cations on murine L-929 fibroblasts, human gingival fibroblasts, and human tissue mast cells were analyzed in vitro. Several metal cations (dose range, from 0.0033 to 1.0 mmol/L) were found to induce dose-dependent inhibition of 3H-thymidine incorporation into cultured fibroblasts. The rank order of potency (lowest observed effect level, LOEL) for L-929 fibroblasts was: Ag+ > Pt4+ > Co2+ > In3+ > Ga3+ > Au3+ > Cu2+ > Ni2+ > Zn2+ > Pd2+ > Mo5+ > Sn2+ > Cr2+. A similar rank order of potency was obtained for primary human gingival fibroblasts: Pt4+ > Ag+ > Au3+ > In3+ > Ga3+ > Ni2+ > Co2+ > Zn2+ > Cu2+ > Cr2+ > Pd2+ > Mo5+ > Sn2+. In primary human mast cells, Ag+ and Au3+ caused dose-dependent toxic histamine release, whereas the other metal cations were ineffective over the dose range tested. To investigate the mechanism of metal cation-induced effects, we performed DNA as well as electron microscopic analyses on cultured fibroblasts. Both the DNA pattern and the ultrastructure of L-929 cells and gingival fibroblasts after exposure to cytopathogenic metal cations revealed signs of necrosis but no signs of apoptosis. Together, our data provide evidence that various metal cations produce dose-dependent cytopathogenic effects in distinct cell types, including human gingival fibroblasts and human tissue mast cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Intracellular-messenger-mediated cation channels in cultured olfactory receptor neurons.

After 2-3 weeks in culture, pupal olfactory receptor neurons from the antennae of male Manduca sexta respond to their species-specific sex pheromone by opening cation channels. These pheromone-dependent cation channels are the only channels previously found in cultured olfactory neurons that promote inward currents at membrane potentials more negative than the resting potential. The pheromone-dependent currents depend on external Ca2+ concentration. They are inwardly rectified with 10(-7) mol l-1 external Ca2+ and linear with 6 mmol l-1 external Ca2+. This paper shows that perfusion of cultured olfactory receptor neurons with GTP gamma S, ATP, inositol 1,4,5-trisphosphate or 10(-6) mol l-1 Ca2+ elicits cation currents resembling the pheromone-dependent cation currents in expressing inward rectification with 10(-7) mol l-1 external Ca2+ and being linear at external Ca2+ concentrations of 2 mumol l-1 or more. Stimulation with protein kinase C also elicits cation currents that share properties with the pheromone-dependent cation currents. All agent-induced cation currents appear to depend either directly or indirectly on Ca2+ concentration.

Adenosine Triphosphate↗
PubMed2001

The effect of metal cation binding on the protein, lipid and retinal isomeric ratio in regenerated bacteriorhodopsin of purple membrane.

The effect of metal cation binding on bacteriorhodopsin (bR) in purple membrane has been examined using in situ attenuated total reflection-Fourier transform infrared difference spectroscopy in aqueous media. It is known that adding metal cations to deionized bR regenerates the purple state from its blue state and recovers the proton pump function. During this process, infrared spectral changes in the frequency region of 1800-1000 cm-1 are monitored. The results reveal that metal cation binding affects the protein conformation, the retinal isomeric composition as well as lipid head groups. It is also observed that metal cation binding induces conformational changes in the alpha 1-helix region of bR, converting the portion of its alpha 1-helical domain into beta-turn or disordered coil. In addition, the influence of Ho3+ binding on the protein and lipid is observed to be larger than that of Ca2+. These results suggest that some of the metal cation binding sites are on the membrane lipid domain, while others could be on the intrahelical domain or interhelical loops where the Asp and Glu are located (binding with their COO- groups). Our results also suggest that the removal of the C-terminal of bR increase the accessibility of the binding site of metal cations, which affects protein conformational structure. All these observations are discussed in terms of the two proposals given in the literature regarding the metal cation binding sites.

Bacteriorhodopsins↗
PubMedDate not supplied

Characterization of cation-pi interactions in aqueous solution using deuterium nuclear magnetic resonance spectroscopy.

Chemical interactions of aromatic organic contaminants control their fate, transport, and toxicity in the environment. Recent molecular modeling studies have suggested that strong interactions can occur between the pi electrons of aromatic molecules and metal cations in aqueous solutions and/or on mineral surfaces, and that such interactions may be important in some environmental systems. However, spectroscopic evidence for these so-called cation-pi interactions has been extremely limited to date. In this paper, cation-pi interactions in aqueous salt solutions were characterized via 2H nuclear magnetic resonance (NMR) spin-lattice relaxation times (T1) and calculations of molecular correlation times (tau(c)) for a series of perdeuterated (d6-benzene) benzene-cation complexes. The T1 values for d6-benzene decreased with increasing concentrations of LiCl, NaCl, KCl, RbCl, CsCl, and AgNO3, with the largest effects observed in the AgNO3 and CsCl solutions. Upon normalizing tau(c) values by solution viscosity effects, an overall affinity trend of Ag+ >> Cs+ > K+ > Rb+ > Na+ > Li+ was derived for the d6-benzene-cation complexes. The ability of Ag+ to complex d6-benzene was significantly reduced upon addition of NH3, which strongly coordinates Ag+ at high pH. Results with d6-benzene, d8-naphthalene, d2-dichloromethane, and d12-cyclohexane in 0.1 M methanolic salt solutions confirmed that spin-lattice relaxation rates are characterizing cation-pi interactions. The relatively strong cation-pi bonding observed between Ag+ and aromatic hydrocarbons probably results from covalent interactions between the aromatic pi electrons and the d orbitals of Ag+, in addition to the normal electrostatic interaction.

Cations↗
PubMed2000

Enhanced cellular uptake and transport of polyclonal immunoglobulin G and fab after their cationization.

Antibodies are poorly transported across cell membranes and biological barriers in vivo. Cationization of antibody molecules by the derivatization of surface carboxyl groups generating primary amino groups could represent a strategy for intracellular antibody delivery. Before cationization of polyclonal colchicine-specific IgG and Fab, using hexamethylenediamine the isoelectric point (pl) of native IgG and Fab (nIgG and nFab) was in the range of 5.9 9.0 and 8.7-9.3, respectively. The pI of cationized IgG and Fab (cIgG and cFab) were both higher at 8.7, 10.3 and 9.5 -11, respectively. The affinity and specificity of both IgG and Fab were not modified by cationization. When HL 60 cells were incubated with the native or cationized 125I-BSA. -IgG and -Fab, the maximal cellular uptake of clgG and cFab was 3.2 and 2.4 times higher than that of nIgG and nFab at an extracellular concentration of 500 ng/ml. Results also indicated that the uptake was dose- and temperature-dependent suggesting absorptive-mediated endocytosis of cationized antibodies by HL 60 cells. Confocal microscopy analysis indicated that the cationized antibodies were present in the plasma membranes and cytoplasm of HL 60 cells. Finally, a study with bovine arterial endothelial monolayer cells showed that the transport of cIgG and cFab through the monolayer cells was 3.3- and 4.3-fold higher for 125I-cIgG and 125I-cFab than those of the corresponding native forms.

Animals↗
PubMedDate not supplied

[Effect of transition metal cations on Na+-Ca2+-exchange in cell membrane].

The possible mechanism of transient metals effect on Na(+)-CA2+ exchange of membrane in excitable and non-excitable cells has been examined on the basis of available literature and personal investigation. Different cations of transient metals can either inhibit or stimulate Na(+)-Ca2+ exchange depending on experimental conditions and their own properties. In some conditions these cations can even be translocated by the exchanger. Metal cations with the highest affinity to O-containing protein groups are able to inhibit the activity of exchanger due to the competition with Ca2+ within the transport site. Metal cations with the highest affinity of S-containing protein groups have stimulated the exchanger owing to their effect on the regulatory site. The total effect of different cations in each case is determined by the effectiveness of all these processes (inhibition, translocation and stimulation) which depends on the affinity of the cations to different protein functional groups. It has been assumed that complex investigation of the effect of different transient metals' cations is necessary for the revealing of Na(+)-Ca2+ exchange mechanism.

Calcium↗
PubMed1999

Polyspecific organic anion transporting polypeptides mediate hepatic uptake of amphipathic type II organic cations.

Hepatic uptake of albumin-bound amphipathic organic cations has been suggested to be mediated by multispecific bile salt and organic anion transport systems. Therefore, we investigated whether the recently cloned rat organic anion transporting polypeptides 1 and 2 as well as the human organic anion transporting polypeptide might be involved in the hepatocellular uptake of bulky type II organic cations. In cRNA-injected Xenopus laevis oocytes, all three carriers mediated uptake of the known type II model compounds N-(4, 4-azo-n-pentyl)-21-deoxy-ajmalinium and rocuronium, whereas the newly synthesized type II model compounds N-methyl-quinine and N-methyl-quinidine were transported only by the human organic anion transporting polypeptide. This carrier-mediated uptake of N-methyl-quinine and N-methyl-quinidine was sodium-independent and saturable with apparent K(m) values of approximately 5 and approximately 26 microM, respectively. In contrast to bulky type II organic cations, more hydrophilic type I organic cations such as tributylmethylammonium and choline were not transported by any of the organic anion transporting polypeptides. These findings demonstrate that organic anion transporting polypeptides can also mediate hepatocellular uptake of type II organic cations, whereas uptake of small and more water-soluble type I cations is mediated by different transport systems such as the organic cation transporters.

Animals↗
PubMed1999

Cationic lipid-mediated gene transfer: current concepts.

Infectious disease, heart disease, cancer, autoimmunity, genetic defects and even traumatic injury may someday be treated with gene therapy and gene transfer strategies. The potential impact of this new technology on human disease has produced optimism and expectation for scientists and lay people alike. As more effort is directed at harvesting the potential of this technology it has become clear that the success or failure of gene therapy will hinge on our ability to manipulate and control the process of gene transfer in somatic cells. Today, somatic gene transfer is accomplished using either viral or non-viral gene transfer methods. The benefits and limitations of each system are aggressively being investigated to determine which characteristics are most compatible with safe and reliable gene transfer. Gene transfer with cationic lipid/plasmid DNA complexes (cationic lipoplexes) has become a popular means of delivering therapeutic genes and is being tested in preclinical and clinical trials. Cationic lipoplexes are easy and inexpensive to produce, they are composed of non-toxic and non-immunogenic precursor, and they have the potential of delivering large polynucleotides into somatic cells. Additionally, these reagents are easily manipulated in the laboratory to incorporate novel biological functions or to produce new formulations that can be screened for in vivo gene transfer activity. The last few years has seen many advances in our understanding of molecular and biological factors that influence cationic lipid-mediated gene transfer. In this review we discuss recent developments in the field of cationic lipid-mediated gene transfer with emphasis on in vivo application where possible. We will consider new discoveries concerning the molecular and cellular events that control the uptake, transit and expression of lipoplexes in somatic cells. Recent biodistribution and pharmacokinetic studies and current concepts regarding the toxicity and immunogenicity of cationic lipoplexes will also be discussed. We also survey some of the many preclinical and clinical trials using cationic lipid-mediated gene transfer, with emphasis on cancer applications.

Animals↗
PubMed1988

Inhibitory effects of cations on the gastric H+, K+ -ATPase. A potential-sensitive step in the K+ limb of the pump cycle.

The presence of a cation inhibitory site on the dephosphoform of the H+, K+ -ATPase was confirmed by comparing the effects of K+ and NH4+ on overall activity and on phosphorylation and dephosphorylation. Inhibition of ATPase activity was pronounced at high cation/ATP ratios, but NH4+ was much less effective. At 60 mM cation, although the ATPase activity was greater in the presence of NH4+ (17.1 mumol/mg.h) as compared to K+ (5.1 mumol/mg.h), dephosphorylation of preformed phosphoenzyme was faster with K+ (2101 min-1) than with NH4+ (1401 min-1). Increasing K+ concentrations at the cytosolic face of the enzyme, at constant ATP, decreased the rate of phosphorylation from 1343 to 360 min-1 at 25 mM K+. Increasing ATP concentrations in the presence of constant K+ concentrations accelerated ATPase activity and increased the steady-state phosphoenzyme level. Therefore, inhibition by cations was due to cation stabilization of a dephospho form of the enzyme at a cytosolically accessible cation-binding site. ATP promoted cation dissociation from this site. In ion-permeable vesicles, increasing K+ concentrations, at constant ATP, activated and then inhibited ATPase activity, with a K0.5(I) of 22 mM. In intact, ion-impermeable inside-out vesicles, in the presence of valinomycin, ATPase activity increased up to 175 mM K+. Collapse of this potential by the addition of the electrogenic protonophore 3,3',4', 5-tetrachlorosalicylanilide restored the K+ inhibition of ATPase activity. Thus, the cation inhibition of the ATPase activity appears to be voltage-sensitive; and hence, its connection to the voltage sensitivity of acid secretion demonstrated in intact gastric mucosa is discussed.

Adenosine Triphosphatases↗
PubMed1988

Exercise-induced microalbuminuria in diabetes is associated with the urinary excretion of cationic proteins.

Urinary protein components, highly cationic in nature (pI 10.9), with apparent molecular weights of 65 kD, 45 kD, and 28 kD were detected in type I diabetic patients before (2/7), during (4/7) and after (1/7) exercise. Based on the apparent isoelectric point and molecular weights, the urinary cationic components in the urines of type I diabetic patients were superimposable to purified cationic proteins derived from human platelets. Furthermore, they also shared common antigenic components as evidenced by the ability of a goat anti-human platelet-derived cationic protein serum to immunoprecipitate the 45 kD protein fraction. The latter induced vascular permeability when injected intradermally in the rabbit's skin. The occurrence of urinary cationic proteins was associated with the significant increase in albumin excretion rate (AER) in diabetic patients. No urinary cationic components were ever detected in the urines of 6 healthy subjects before, during, or after exercise. The possible pathogenetic relevance of the urinary excretion of cationic proteins in diabetic AER is discussed.

Adolescent↗
PubMed1986

The stimulation by monovalent cations of the amidase activity of bovine des-1-41 light chain activated protein C.

The kinetic properties of the activation by monovalent cations of the amidolytic activity of bovine des-1-41 light chain activated protein C have been examined. With the cations Cs+, K+, Li+, and Tl+, a single cation site, or class of sites, has been found to be responsible for the stimulation observed, with kinetic Ka values of 98-110, 180-210, 300-310, and 14-16 mM, respectively. The mechanism proposed for participation of these cations in the enzyme reaction involves an ordered addition, with the binding of cation preceding the binding of the amide substrate. On the other hand, the kinetic properties of this same activation by Na+ are consistent with either two cation sites, or classes of sites, of importance. Once again, however, the mechanism of the reaction appears to be of the ordered type, with cation binding occurring prior to substrate binding.

Amidohydrolases↗
PubMed1985

Effect of alterations in glomerular charge on deposition of cationic and anionic antibodies to fixed glomerular antigens in the rat.

Reduction of the negative charge of the glomerular capillary wall alters its charge- and size-selective properties. To investigate the effect of alteration in glomerular charge properties on antibody localization, we prepared cationic and anionic fractions of antibodies to subepithelial and glomerular basement membrane (GBM) antigens, and compared their deposition in normal rats and rats treated with protamine sulfate or aminonucleoside of puromycin to reduce capillary wall charge. IgG antibodies were eluted from kidneys of rats with active Heymann's nephritis (AICN), passive Heymann's nephritis (PHN), or anti-GBM nephritis (NTN), separated into cationic and anionic fractions, and radiolabeled with iodine 125 or iodine 131. Relative antibody content of each fraction was determined by incubation with an excess of glomerular antigen. Varying amounts of cationic and anionic IgG eluted from kidneys of rats with AICN or PHN were injected into 24 normal or protamine sulfate-treated rats. Glomerular binding of all antibodies was highly correlated with IgG delivery to the kidney. The ratio of cationic to anionic antibody deposited in the glomeruli of normal rats after 4 hours was 1.08 +/- 0.07 for AICN eluate and 0.37 +/- 0.04 for PHN eluate. The ratios were not significantly different in animals pretreated with protamine sulfate (1.15 +/- 0.06 and 0.44 +/- 0.06, respectively; P greater than 0.05). Varying amounts of cationic and anionic IgG eluted from kidneys of rats with NTN were injected into 10 normal rats and four rats treated with aminonucleoside of puromycin. Glomerular binding of antibody was again highly correlated with IgG delivery to the kidney. The ratio of cationic to anionic antibody deposited in the glomeruli of normal rats after 1 hour was 1.03 +/- 0.06, and was not significantly altered in rats treated with aminonucleoside of puromycin (1.05 +/- 0.03, P greater than 0.5). Proteinuria in PHN rats was also unaffected by treatment with protamine sulfate for 5 days (controls: 68 +/- 21 mg/day; protamine sulfate-treated: 65 +/- 14 mg/day; n = 25, P greater than 0.08). These results demonstrate that treatment to reduce glomerular polyanion does not significantly alter the ratio of cationic to anionic antibodies to fixed glomerular antigens that deposit in the glomerulus, or reduce proteinuria caused by deposition of antibody to a fixed subepithelial antigen.

Animals↗