Preparation of antibody-ferritin conjugates for immunoelectron microscopy

Volume electron microscopy for genetically and molecularly defined neural circuits

The brain networks responsible for adaptive behavioral changes are based on the physical connections between neurons. Light and electron microscopy have long been used to study neural projections and the physical connections between neurons. Volume electron microscopy has recently expanded its scale of analysis due to methodological advances, resulting in complete wiring maps of neurites in a large volume of brain tissues and even entire nervous systems in a growing number of species. However, structural approaches frequently suffer from inherent limitations in which elements in images are identified solely by morphological criteria. Recently, an increasing number of tools and technologies have been developed to characterize cells and cellular components in the context of molecules and gene expression. These advancements include newly developed probes for visualization in electron microscopic images as well as correlative integration methods for the same elements across multiple microscopic modalities. Such approaches advance our understanding of interactions between specific neurons and circuits and may help to elucidate novel aspects of the basal ganglia network involving dopamine neurons. These advancements are expected to reveal mechanisms for processing adaptive changes in specific neural circuits that modulate brain functions.

FerriTag is a new genetically-encoded inducible tag for correlative light-electron microscopy

A current challenge is to develop tags to precisely visualize proteins in cells by light and electron microscopy. Here, we introduce FerriTag, a genetically-encoded chemically-inducible tag for correlative light-electron microscopy. FerriTag is a fluorescent recombinant electron-dense ferritin particle that can be attached to a protein-of-interest using rapamycin-induced heterodimerization. We demonstrate the utility of FerriTag for correlative light-electron microscopy by labeling proteins associated with various intracellular structures including mitochondria, plasma membrane, and clathrin-coated pits and vesicles. FerriTagging has a good signal-to-noise ratio and a labeling resolution of approximately 10 nm. We demonstrate how FerriTagging allows nanoscale mapping of protein location relative to a subcellular structure, and use it to detail the distribution and conformation of huntingtin-interacting protein 1 related (HIP1R) in and around clathrin-coated pits.

A new method of the immunohistochemical detection of cellular antigens for light and electron microscopy

A new immunohistochemical method for light and electron microscopy of tissue- and cell-specific antigens by using ferric colloid-labeled antibody is presented. The antibodies labeled with the cationic cacodylate ferric colloid are stable and bind specifically to the target antigens to show clearly the site of antigens in tissue sections and on free cells by Prussian blue reaction for light microscopy and by the specific figure of electron opaque ferric colloid particles for electron microscopy. The staining procedure is very simple and it gives clear picture. So the method will be of beneficial for general laboratory use in immunohistochemical researches.

Arrangement of peptidoglycan in the cell wall of Staphylococcus spp

The arrangement of peptidoglycan in the cell wall of Staphylococcus was observed with the newly developed freeze-fracture technique, using n-octanol instead of water as the freezing medium. The replica of the trichloroacetic acid-extracted cell wall (TCA-wall) showed two areas. One of them has a concentric circular structure, a characteristic surface structure of the staphylococcal cell wall, and the other showed an irregular and rough surface. The chemical analysis of the wall revealed that the TCA-wall consisted of mostly peptidoglycan. By digesting the TCA-wall with lysozyme, the circular structures were greatly disturbed, and they disappeared after 60 min of treatment. From these observations it can be expected that the peptidoglycan is arranged in a concentric circular manner in the newly generated cell wall of Staphylococcus.

Evidence for the sorting of endocytic vesicle contents during the receptor-mediated transport of IgG across the newborn rat intestine

Fc receptors on the luminal membranes of intestinal epithelial cells in the neonatal rat mediate the vesicular transfer of functionally intact IgG from the intestinal lumen to the circulation. In addition, there is a low level of nonselective protein uptake, but in this case transfer does not occur. To determine whether a specialized class of endocytic vesicles could account for the selective transfer of IgG, mixtures of IgG conjugated to ferritin (IgG-Ft) and unconjugated horseradish peroxidase (HRP) were injected together into the proximal intestine of 10-d-old rats, and the cellular distribution of these two different tracers was determined by electron microscopy. Virtually all apical endocytic vesicles contained both tracers, indicating simultaneous uptake of both proteins within the same vesicle. However, only IgG-Ft bound to the apical plasma membrane, appeared within coated vesicles at the lateral cell surface, and was released from cells. HRP did not bind to the luminal membrane and was not transferred across cells but was confined to apical lysosomes as identified by acid phosphatase and aryl sulfatase activities. To test the possibility that the binding of IgG to its receptor stimulated endocytosis, HRP was used as a fluid volume tracer, and the amount of HRP taken up by cells in the presence and absence of IgG was measured morphologically and biochemically. The results demonstrate that endocytosis in these cells is constitutive and occurs at the same level in the absence of IgG. The evidence presented indicates that the principal selective mechanism for IgG transfer is the binding of IgG to its receptor during endocytosis. Continued binding to vesicle membranes appears to be required for successful transfer because unbound proteins are removed from the transport pathway before exocytosis. These results favor the proposal that IgG is transferred across cells as an IgG-receptor complex.

Purification and characterization of surface fibrils from taxonomically typical Actinomyces viscosus WVU627

Fibrils of Actinomyces viscosus WVU627 (numerical taxonomy cluster 1) were obtained by homogenization and purified by ultrafiltration, ammonium sulfate precipitations, gel filtration, and ion-exchange chromatography. Electron microscopy and resolution of a single band by sodium dodecyl sulfate-polyacrylamide gel electrophoresis attested to the purity of the preparation. Purified fibrils were composed mainly of protein; small quantities of carbohydrate and phosphorus were detected. Immunoelectrophoresis revealed only a single precipitable antigen, which migrated slightly toward the anode, in reactions between purified fibrils and antiserum raised against either whole bacterial cells or the purified fibrils themselves. Immunoelectron microscopy with ferritin-conjugated antifibril antibody hemagglutination inhibition, and bacterial agglutination tests demonstrated that fibrils of Actinomyces viscosus cluster 1 strains shared some common antigens with clusters 2, 3, 4 and 6, but did not cross-react with typical Actinomyces naeslundii of cluster 5. Stability tests revealed that after heat or alkali treatment, the fibrils lost their antigenicity and disappeared from electron micrographs. They were affected less by sodium dodecyl sulfate, sonic, or acid treatments.

An immunocytochemical method for histamine detection

An anti-histaminic immune serum, prepared in New Zealand male rabbits by immunization with a chemospecific antigen (diazotized para-amino-benzoyl-azohistamine) was labeled with fluorescein isothiocyanate for the purpose of histamine detection or was employed for demonstration of histamine using fluorescein-labeled protein A. The IgG fraction of the hyperimmune serum was isolated, purified, and tested for specificity by binding to 3H-histamine or to histamine-containing or histamine-treated cells. Histological preparations used for detection of histamine should be fixed preferably in Carnoy solution. The procedure can also be employed for ultra-histochemical detection of histamine, using ferritin-conjugated antibody or the peroxidase technique.

Changes in immunoferritin labeling of Rickettsia tsutsugamushi after serial cultivation in 60Co-irradiated BHK cells

The immunolabeling characteristics of Rickettsia tsutsugamushi (Gilliam strain) were examined by using a purified immunoglobulin G fraction of antibody to R. tsutsugamushi raised in rabbits. Formalin-fixed rickettsiae were reacted with this antibody and then with ferritin-conjugated goat anti-rabbit Fc antibody. R. tsutsugamushi cultivated in yolk sacs was used to raise antibody for this study. When rickettsiae in BHK-21 cells infected from yolk sac seed material were immunoferritin labeled, the binding of ferritin was found to be dense and uniform on the outer surface of the rickettsiae in disrupted host cells. Immunolabeling of purified suspensions of extracellular rickettsiae resulted in the uniform ferritin labeling of the microorganism. Aggregation of these rickettsiae by antibody appeared to depend upon the purity of the pellets. Immunoferritin labeling examined at high magnification revealed ferritin very close to the outer dense leaflet of the outer membrane. On some rickettsiae or on focal sites of others, the labelin; was several ferritin particles thick, suggesting the presence of a thick coating. The immunoferritin labeling of R. tsutsugamushi during successive serial passages in BHK-21 cells revealed decreased labeling with each passage, and by the 10th passage there was no detectable labeling. However, these rickettsiae inoculated back into yolk sacs regained their immunoferritin labeling. R. tsutsugamushi passed back into yolk sacs after four serial propagations in BHK-21 cells regained their labeling on the first passage in yolk sacs. However, rickettsiae from the 20th serial passage in BHK-21 cells required five passages in yolk sacs to reestablish their previous labeling affinity. Rickettsiae which did not label after 20 passages in BHK cells regained some of their labeling characteristics when sonicated. Antibody against rickettsiae cultivated in BHK-21 cells continued labeling rickettsiae even after 9 serial passages in BHK-21 cells.

Identification of dynein as the outer arms of sea urchin sperm axonemes

The location of dynein, the main flagellar ATPase, within the sea urchin sperm axoneme was investigated by the use of immunofluorescence and immunoelectron microscopy, employing an antiserum against a tryptic fragment of dynein 1 (Fragment 1A) purified from sea urchin sperm flagella. The axonemes were found to be stained with the antiserum when examined by an indirect immunofluorescence technique. Immunoelectron microscopy with the antiserum and a ferritin-conjugated IgG fraction of goat antiserum to rabbit IgG revealed that, among the structures within the axoneme, only the outer arms were labeled with ferritin particles. With either the normal serum or antiserum absorbed with Fragment 1A, there were no ferritin particles within the axonemes. When the outer arms were extracted with 0.5 M NaCl, leaving the inner arms intact, again no ferritin dots were detected. Furthermore, it was found that the outer arm on the no. 5 doublet microtubule, which connects with the extra arm projection backward from the no. 6 doublet, had no attached ferritin particles. From these observations, it can be concluded that the outer arm consists of dynein (at least dynein 1) and that Fragment 1A, containing the active site for ATPase activity of dynein 1, is located at the distal end of the outer arms. The significance of the present findings is considered in connection with flagellar movement.

Staphylococcal protein A in immunoferritin techniques

Protein A (pA) of Staphylococcus aureus, by virtue of its reactivity with the Fc portion of a variety of mammalian immumoglobulins (IgG), can be used for electron-microscopical immunoferritin techniques. The conjugation of pA with ferritin (pA-F) by means of bis(4-fluoro-3-nitrophenyl) sulfone results in a highly specific marker for IgG in indirect labeling experiments. Native pA can be used as a noncovalent bridging agent between specific antibodies and antiferritin capturing the marker molecule. The use of pA and pA-F is demonstrated with a model system involving human erythrocytes and two rabbit antisera directed against different surface antigens of the human erythrocyte membrane.

Electron microscopic observations on the H antigen sites of human erythrocytes using ferritin antibody conjugates

Using immunoelectron microscopy, the distribution of the H antigen sites on human erythrocytes was observed in 40 samples of adult, newborn and fetal blood of different ABO phenotypes. The attached ferritin particles indicating the H antigen sites conspicuously varied in number from cell to cell in every specimen. The number of H antigen sites per single red cell was estimated on an average for each sample as follows: O, 3 X 10(5); B, 2 X 10(5); A1, 1.5 X 10(5); A1B, 10(5); A2B, 1.5 X 10(5); Ax, 2.5 X 10(5); AxB, 10(5); Bm, 4 X 10(5); Bw(leukemia), 4 X 10(5); O(newborn), 2.5 X 10(5); B(newborn), 3 X 10(5); A1(newborn), 1.5 X 10(5); A1B(newborn), 2 X 10(5); A1B(fetus), 10(5). The cells in each sample were divided into six cell-populatons according to the number of H antigen sites present. The ratios of distribution of such cell populations are compared for all samples.

Two improved methods for preparing ferritin-protein conjugates for electron microscopy

Two improved procedures were developed for activating ferritin so that the ferritin could be covalently linked to antibodies. One procedure involved use of a water-soluble carbodiimide and N-hydroxysuccinimide to prepare ferritin-containing activated esters. The other involved activation of the ferritin with excess glutaraldehyde. The ferritin-antibody conjugates prepared with the two procedures were shown to have a number of properties which made them suitable for locating antigenic components in cells.

Slime of Pseudomonas aeruginosa: in vivo production

Indirect hemagglutination inhibition tests were employed to detect slime in concentrations as low as 1 mug/ml. Increasing concentrations of slime resulted in proportionately greater inhibition of hemagglutination. Peritoneal aspirates and plasma of mice injected with slime were shown to exhibit the inhibitory activity of slime. The rapid dissemination of slime into the peripheral circulation was also indicated by the hemagglutination of mouse erythrocytes by specific anti-slime serum. By similar methods, the inhibitory activity of slime was also detected in peritoneal aspirates and plasma of mice infected with lethal doses of viable Pseudomonas aeruginosa. Furthermore, the inhibitory activity was found to increase with time after viable cell infection, whereas such increases were not detected after the injection of heat-killed organisms. Ferritin-labeled slime antibodies were found to completely surround cells of Pseudomonas aeruginosa obtained from the peritoneal cavity of mice 5 h postinfection.

Studies on the distribution of surface immunoglobulins of human B-lymphocytes

Normal human peripheral blood lymphocytes were studied with fluorescent anti-immunoglobulin antibodies and shown to have a patchy distribution of immunoglobulin on their surfaces that does not form a cap after complexing with antibody. Use of freeze-etch electron microscopy confirmed the distribution of immunoglobulin in isolated patches on the membrane. Evidence is presented that this distribution may explain the absence of capping of these human cells as compared with mouse B-lymphocytes.Studies of the metabolism of antibody bound to the cell surface revealed rapid shedding of complexes from the cell and also rapid endocytosis with subsequent degradation of the antibody. Several attempts to alter this distribution of immunoglobulin on the surface were unsuccessful. Possible mechanisms by which cell surface elements may be organized are discussed, as well as the significance of the results in terms of the immune response and the classification of certain lymphoproliferative diseases.

Intestinal transport of antibodies in the newborn rat

Evidence has been reported that the proximal small intestine of the neonatal rat selectively transports antibodies into the circulation. This study describes the morphology of the absorptive epithelial cells in this region of the intestine and their transport of several immunoglobulin tracers: ferritin-conjugated immunoglobulins (IgG-Ft) and antiperoxidase antibodies. Cells exposed to rat IgG-Ft bound the tracer on the membrane of tubular invaginations of the apical cell surface. Tubular and coated vesicles within the cell also contained the tracer, as did the intercellular spaces. Uptake of tracer was highly selective and occurred only with rat or cow IgG-Ft; when cells were exposed to chicken IgG-Ft, ferritin-conjugated bovine serum albumin, or free ferritin, tracer did not enter the cell or appear in the intercellular spaces. Experiments with rat and chicken antiperoxidase showed a similar selective uptake and transport of only the homologous antibody. When cells from the distal small intestine were exposed to the tracers, all tracers were absorbed nonselectively but none were released from the cells. Cells from the proximal small intestine of the 22-day-old rat failed to absorb even rat IgG-Ft. A model is presented for selective antibody transport in proximal cells of the neonatal rat in which antibodies are selectively absorbed at the apical cell surface by pinocytosis within tubular vesicles. The antibodies are then transferred to the intercellular space within coated vesicles. Distal cells function only to digest proteins nonselectively.

Ligand-induced movement of lymphocyte membrane macromolecules. II. Mapping of surface moieties

Anti-immunoglobulin (Ig) coupled to ferritin or hemocyanin was used to map the distribution of Ig molecules on lymphocytes derived from bone marrow (B lymphocytes) by freeze-etching. The labeled anti-Ig was distributed all over the membrane in the form of random interconnected patches forming a lacy, continuous network. This was the pattern of lymphocytes labeled at 4 degrees C with the anti-Ig. After warming at 37 degrees C, the labeled molecules concentrated into a single area of the cell (forming the cap) and were rapidly internalized in small vesicles Freeze-etching showed close packing of the labeled molecules in the cap area. There was evidence that in the cap area the Ig molecules were exfoliated from the plane of the membrane, suggesting that the Ig may be superficial to the bilipid layer, or weakly anchored to the membrane. Similar studies were made using antibodies to histocompatibility antigens. Thymocytes were labeled with anti-H-2 and ferritin anti-Ig at 4 degrees C. Freeze-etching showed large patches scattered over the membrane and separated from each other by several thousand angstroms. This distribution may, in part, explain why H-2 antigens do not readily form a cap; the large patches are beyond the reach of even a double ligand (sandwich) reaction. The antigens that reacted with heterologous anti-lymphocyte globulin (ALG) were found in small noninterconnected clusters a few hundred angstroms apart. Such clusters presumably cannot be linked by a single antibody but can by a sandwich (ligand to ligand-antigen) reaction. In previous studies it was found that ALG antigens form a cap only after a sandwich reaction. Finally, the receptors for concanavalin A (Con A) were found in a lacy, irregular interconnected, random network. The spatial distribution of these moieties on the membrane may, in great part, determine their movement after reaction with one or two ligands.

Immunoperoxidase localization of herpes zoster virus and simian virus 40 in cell culture

The immunoperoxidase technique was used in an electron microscopy study to localize the virions of herpes zoster virus and simian virus 40 in cell cultures. Intranuclear and intracytoplasmic virions of herpes zoster virus were easily and specifically identified due to intense staining by the finely granular, black reaction product. With simian virus 40, intranuclear virions were not stained, whereas intracytoplasmic particles appeared densely black. There was essentially no background staining. Advantages of this technique over the ferritin-labeled antibody method include simpler preparative procedures for reagents, greater penetrability of the antibody conjugate, and internal amplification which substantially improves the ability to localize sites of antigen-antibody reaction. We believe that the immunoperoxidase method can be successfully applied to a wide variety of problems involving viral antigens.

Detection of cholesterol in cell membranes by use of bacterial toxins

A method is described for the detection of cholesterol in membranes from erythrocytes, mycoplasmas, and bacterial cells by a ferritin-labeling technique. Membranes treated with cereolysin, a bacterial hemolysin which specifically binds to cholesterol, and then treated with ferritin-antitetanolysin, were specifically ferritin-labeled for cholesterol. A similar antigen-antibody system, streptolysin O-ferritin-antistreptolysin, was also used successfully with erythrocyte membranes. There was an uneven distribution of ferritin in erythrocyte membranes suggesting that the distribution of cholesterol may not be entirely random. Mycoplasma gallisepticum was intensely labeled, but Acholeplasma laidlawii with or without cholesterol in the membranes was not labeled, suggesting an unusual location for cholesterol in A. laidlawii membranes. As controls, two of three species of bacterial membranes lacking cholesterol were not ferritin-labeled.

Localization of ferritin-conjugated anti-fibrin-fibrinogen in platelet aggregates produced in vitro

A ferritin-conjugated anti-fibrin/fibrinogen was localized by means of light and electron microscopy in artificial in vitro thrombi formed in the presence of the labeled antibody, and in preformed ADP-induced platelet aggregates. The ferritin was distributed throughout the central and peripheral regions of the columns of aggregated platelets in the thrombi. In the preformed ADP aggregates, ferritin was deposited only by infiltration from surrounding plasma and was confined to the periphery of the columns. The even distribution of ferritin in the central zone of the platelet columns of the thrombi indicated a specific reaction had occurred before or during thrombus formation unrelated to infiltration of plasma. In the artificial thrombi, the ferritin-labeled antibody was localized on the surface layer of platelets and on the bridging structures composed of the combined surface layers in the narrow spaces between cohesive platelets. Vesicles and alpha granules within the platelets also were tagged. The absence of obvious fibrin between narrow interspaces and within the platelets indicated that the antibody had reacted with fibrinogen or partly polymerized fibrin at these sites. Many invaginations of the platelet membrane containing dense fibrillar material were interpreted to be alpha granules discharging their contents during the "release reaction" at the time of aggregation. This material, which was tagged by the ferritin-conjugated antibody, merged with the interplatelet bridges to suggest that released fibrinogen from within the platelet contributed to the structural bond and strengthened it. A layer of dense fibrin and altered platelets in the periphery of the columns of aggregated platelets in the artificial thrombi contained the platelets and limited further growth of the aggregates. The fibrin was thought to be derived from infiltrated plasma as well as from released intraplatelet fibrinogen. Platelet fibrinogen thus appeared to take part both in the cohesion of aggregated platelets and in the stabilization of the aggregates formed.

Transmission of human gamma-globulin to rabbit foetus and its inhibition by conjugation with ferritin

The transmission of a ferritin—human γ-globulin conjugate across the rabbit yolk sac splanchnopleur has been investigated by means of the fluorescent antibody technique, and a comparison made with the transmission of the separate components. Ferritin alone was not transmitted to the foetal circulation and neither was the conjugate, whereas human γ-globulin alone was readily transmitted. However, both the conjugate and the separate components were readily transmitted to the exocoelomic and amniotic fluids by traversing the paraplacental chorion. These results are discussed in the light of a proposed hypothesis to explain selective transfer of proteins.

Isolation and characterization of immunoferritin conjugates. II. Antibody binding capacity in vitro

The antibody activity of the IgG fraction of anti-HSA from the rabbit was compared with the antibody activity of the same fraction conjugated to ferritin. No significant loss of antibody activity due to the conjugation to ferritin could be demonstrated.

Isolation and characterization of immunoferritin conjugates. I. The molecular ratio

¹²⁵I-labelled γ-globulin was conjugated to ferritin for the determination of the molecular ratio in ferritin—γ-globulin conjugates. Equimolar ratios were found in all conjugates free of uncoupled γ-globulin.

Host antigens in schistosomiasis

It has previously been shown that adult schistosomes excite an immune response in the rhesus monkey but do not themselves succumb to this response. Furthermore, schistosomes are known to persist in the blood of man and experimental animals for long periods. These findings point to the evolution of a special mechanism for circumventing the immune defences of the host. The present paper sets out evidence which suggests that this mechanism involves the incorporation of host antigens at the surface of the adult worm. When adult worms, which had been grown in mice (‘mouse worms’), were transferred into the hepatic portal systems of normal monkeys, a large proportion (84 %) were recovered alive 1 to 6 weeks later. Worms recovered after 1 week were pale and shrunken and the females had ceased egg production; worms recovered after 6 weeks were normal and egg production had been resumed. Evidently, the transferred worms find difficulty at first in adapting to their new host species, but in time they are able to adapt fully. In contrast, when mouse worms were transferred to monkeys previously immunized against normal mouse tissues (anti-mouse monkeys), very few of these worms survived. Indeed, when the monkeys were immunized against mouse spleen and liver cells or erythrocytes, combined with Freund’s complete adjuvant, the transferred mouse worms were completely destroyed. This result indicates that the worms grown in mice had mouse antigens closely associated with them, and that on transfer to anti-mouse monkeys, the worms were destroyed by the ensuing immunological reaction. This immunity was passively transferred to normal monkeys by means of serum; thus the immunity is largely antibody-mediated. Most of the mouse worms died between 7 and 25 h after transfer. The immune reaction was directed mainly against the tegument of the worm, causing breaks in the plasma mem­brane and vacuolation and subsequent degeneration of the underlying syncytium. The mixed agglutination reaction and the use of a ferritin-labelled antiserum combined with electron microscopy confirmed that host antigens were located at the surface of the worm. The antigens appear to be host species-specific; worms which were grown in monkeys or libyan jirds survived normally when transferred to anti-mouse monkeys. There is evidence that the antigens may readily be exchanged between host and parasites. Mouse worms which were transferred to a normal monkey and then transferred after 7 days to an anti-mouse monkey survived as well as monkey worms. Evidently the mouse worms had lost their mouse antigens during this period, perhaps exchanging them for monkey antigens. Three days in a normal monkey was not sufficient, however, for all of the mouse worms to lose their mouse antigens. It is suggested that these host antigens are synthesized by the host, but that they become firmly bound to or incorporated in the tegument. It is conceivable that these antigens serve to disguise the worms as host tissue, thus preventing their rejection by the immune defences of the host. This hypothesis provides an explanation for the apparent anomalies, referred to earlier: the insusceptibility of adult worms to the immune response which they are known to provoke, and their long persistence in the blood, an immunologically hostile environment.

Use of hybrid antibody with anti-gamma-G and anti-ferritin specificities in locating cell surface antigens by electron microscopy

Hybrid antibody [F(ab')(2)] with dual specificity for mouse gammaG and ferritin was prepared from the corresponding rabbit antisera, providing a precise reagent for locating mouse gammaG on cell surfaces. Viable cells were exposed successively to (a) mouse antibody to a cell surface antigen, (b) the rabbit hybrid antibody, and (c) ferritin, before preparation for electron microscopy. This method of See PDF for Structure. labeling is sensitive and specific and clearly lends itself to the introduction of visual markers other than ferritin. Other advantages are uniformity of labeling, ease of purification of the reagent, and circumvention of the many drawbacks arising from coupling ferritin to antibody chemically.

Ultrastructural localization of the third and fourth components of complement on complement-cell complexes

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Electron microscopic localization of the nephrotoxic antibody in the glomeruli of the rat after intravenous application of purified nephritogenic antibody-ferritin conjugates

Nephritis in rats was induced by intravenous injection of purified ferritin-conjugated rabbit and duck nephrotoxic globulin. Using the fluorescent antibody technique, the same capillary pattern was found as that in glomeruli of rats receiving uncoupled nephrotoxic globulin. Electron microscopy revealed a heavy accumulation of the basement membrane-fixed antibody almost exclusively at the endothelial side. A higher concentration of ferritin was demonstrable in the peripheral basement membrane. The once-fixed antibody remained at the site of reaction though decreasing with time. The half-disappearance time seemed to be shorter than that of the uncoupled nephrotoxic globulin. No difference in localization was observed between rabbit and duck antibody. At least 40 basement membrane-fixed antibody molecules from the rabbit per 3000 mmicro(2) of filtration surface were needed to cause immediate nephritis. To induce nephritis using duck antibody, a greater number of basement membrane-fixed antibody seemed to be necessary. No evidence of specific reaction with constituents of glomerular cells was obtained.

Enzyme-labeled antibodies for the light and electron microscopic localization of tissue antigens

Enzymes, either acid phosphatase or horseradish peroxidase, were conjugated to antibodies with bifunctional reagents. The conjugates, enzymatically and immunologically active, were employed in the immunohistochemical localization of tissue antigens utilizing the reaction product of the enzymatic reaction as the marker. Tissues reacted with acid phosphatase-labeled antibodies directed against basement membrane were stained for the enzyme with Gomori's method, and those reacted with peroxidase-labeled antibody were stained with Karnovsky's method. The reaction products of the enzymes localized in the basement membrane. Unlike the preparations of the fluorescent antibody technique, enzyme-labeled antibody preparations were permanent, could be observed with an ordinary microscope, and could be examined with the electron microscope. In the latter, specific localization of antibody occurred in the basement membrane and in the endoplasmic reticulum of cells known to synthesize basement membrane antigens. The method is sensitive because of the amplifying effect of the enzymatic activity. The ultrastructural preservation and localization were better with acid phosphatase-labeled antibody than with peroxidase-labeled antibody, but acid phosphatase conjugated antibody was unstable and difficult to prepare. Peroxidase-antibody conjugates were stable and could be stored for several months at 4 degrees C, or indefiniely in a frozen state.