Idiotypic analysis of anti-I-Ak monoclonal antibodies. II. Detection of shared idiotopes on syngeneic BALB/c and allogeneic A.TH-derived anti-I-Ak mAb by BALB/c-derived anti-I-Ak anti-idiotypic mAb

The IA2, IIID1, and VC6 BALB/c-derived anti-11-5 anti-idiotypic (anti-Id) monoclonal antibodies (mAb) described in the companion paper were used to study the idiotopes expressed by a panel of 13 anti-I-Ak and 10 anti-I-Ek mAb. IA2 and IIID1, which detect binding-site-related idiotopes of the syngeneic BALB/c-derived 11-5 mAb, each react with public idiotope(s) (IdX) of two allogeneic A.TH-derived anti-I-Ak mAb (8B and 39J). VC6, which detects an 11-5 idiotope that differs from the IA2 and IIID1 idiotopes, binds to the 8B but not the 39J mAb. The three anti-Id mAb examined do not bind to idiotopes on 11 other anti-I-Ak or to 10 other anti-I-Ek mAb tested. These data demonstrate that mice immunized with a murine anti-I-Ak mAb probably produce syngeneic anti-IdX serum antibodies. Furthermore, they suggest that the 11-5 IdX markers identified are shared by alloantibodies of the BALB/c (Igh1a) and A.TH (Igh1e) mouse strains and may be expressed independently of Igh-C allotype markers. The sharing of idiotopes between the 11-5, 8B (anti-Ia.2), and 39J (anti-Ia.19) mAb led us to reinvestigate the antigenic specificity of the 11-5 mAb and the genetic complexity of the serologically detectable Ia.2 and Ia.19 epitopes present on I-Ak molecules. Two main points emerge from these studies. First, the 11-5 BALB/c-derived anti-I-Ak mAb, previously considered to have an anti-Ia.2 specificity, was shown by direct binding and competition binding assays to possess instead a reactivity pattern more compatible with that of an anti-Ia.19 mAb. Second, the anti-Ia.2 and anti-Ia.19 mAb, which were provisionally considered to bind epitopes in a single region of an I-Ak molecule, termed epitope cluster IV, actually define at least four different subgroups of this cluster. These subgroups are designated as IV A-D, and IV D is detected by the 11-5 and 39J anti-Ia.19 mAb. This tentative subdivision of I-Ak epitope cluster IV suggests there exists a minimum of seven topologically distinguishable regions of an I-Ak molecule that give rise to polymorphic allodeterminants, some or all of which may mediate lymphocyte interaction.

Idiotypic analysis of anti-I-Ak monoclonal antibodies. II. Detection of shared idiotopes on syngeneic BALB/c and allogeneic A.TH-derived anti-I-Ak mAb by BALB/c-derived anti-I-Ak anti-idiotypic mAb

The IA2, IIID1, and VC6 BALB/c-derived anti-11-5 anti-idiotypic (anti-Id) monoclonal antibodies (mAb) described in the companion paper were used to study the idiotopes expressed by a panel of 13 anti-I-Ak and 10 anti-I-Ek mAb. IA2 and IIID1, which detect binding-site-related idiotopes of the syngeneic BALB/c-derived 11-5 mAb, each react with public idiotope(s) (IdX) of two allogeneic A.TH-derived anti-I-Ak mAb (8B and 39J). VC6, which detects an 11-5 idiotope that differs from the IA2 and IIID1 idiotopes, binds to the 8B but not the 39J mAb. The three anti-Id mAb examined do not bind to idiotopes on 11 other anti-I-Ak or to 10 other anti-I-Ek mAb tested. These data demonstrate that mice immunized with a murine anti-I-Ak mAb probably produce syngeneic anti-IdX serum antibodies. Furthermore, they suggest that the 11-5 IdX markers identified are shared by alloantibodies of the BALB/c (Igh1a) and A.TH (Igh1e) mouse strains and may be expressed independently of Igh-C allotype markers. The sharing of idiotopes between the 11-5, 8B (anti-Ia.2), and 39J (anti-Ia.19) mAb led us to reinvestigate the antigenic specificity of the 11-5 mAb and the genetic complexity of the serologically detectable Ia.2 and Ia.19 epitopes present on I-Ak molecules. Two main points emerge from these studies. First, the 11-5 BALB/c-derived anti-I-Ak mAb, previously considered to have an anti-Ia.2 specificity, was shown by direct binding and competition binding assays to possess instead a reactivity pattern more compatible with that of an anti-Ia.19 mAb. Second, the anti-Ia.2 and anti-Ia.19 mAb, which were provisionally considered to bind epitopes in a single region of an I-Ak molecule, termed epitope cluster IV, actually define at least four different subgroups of this cluster. These subgroups are designated as IV A-D, and IV D is detected by the 11-5 and 39J anti-Ia.19 mAb. This tentative subdivision of I-Ak epitope cluster IV suggests there exists a minimum of seven topologically distinguishable regions of an I-Ak molecule that give rise to polymorphic allodeterminants, some or all of which may mediate lymphocyte interaction.

Electron microscopic and hydrodynamic studies of protein A-immunoglobulin G soluble complexes

The soluble complexes formed by reacting staphylococcal protein A (SpA) with rabbit immunoglobulin G (IgG) antibodies were characterized by hydrodynamic and electron microscopic methods. In moderate SpA excess, equilibrium mixtures of SpA and rabbit IgG formed four discrete complexes that sedimented at approximately 7, 10, 13, and 15S. The putative complexes were visible by electron microscopy and appeared to contain one, two, three, and approximately five molecules of IgG. Probably because of its elongated shape, SpA was not clearly visible in these mixtures or in control preparations of SpA alone. Both native IgG and IgG modified by cleavage of its single-hinge disulfide bond formed similar complexes on interaction with SpA. It was possible to resolve heterogeneous mixtures of IgG-SpA complexes by using an analytical ultracentrifuge equipped with a photoelectric scanner interfaced to a small computer. The relative concentrations and sedimentation velocities of different complexes in a mixture were determined from computer-generated integral and derivative plots. Both hydrodynamic and electron microscopic methods revealed that the distribution of complexes was sensitive to the IgG to SpA molar ratio. The relative amounts of faster complexes increased as the IgG to SpA molar ratio was increased. Surprisingly, when the IgG to SpA molar ratio was greater than or equal to 2, the complexes were converted into a unique 17S complex. This rather unprecedented transformation was reversible: the addition of excess SpA caused the dissociation of the 17S complex into a mixture of the 7, 10, 13, and 15S structures. The average translational diffusion coefficient of the 17S complex was 2.62 +/- 0.13 Ficks. In the electron microscope, the complex appeared to be exceptionally compact with an average diameter of 287 A. The stoichiometry of the 17S complex, together with sedimentation equilibrium, diffusion, and electron microscopic measurements, indicated that it is composed of four molecules of IgG and two molecules of SpA.

Electron microscopic and hydrodynamic studies of protein A-immunoglobulin G soluble complexes

The soluble complexes formed by reacting staphylococcal protein A (SpA) with rabbit immunoglobulin G (IgG) antibodies were characterized by hydrodynamic and electron microscopic methods. In moderate SpA excess, equilibrium mixtures of SpA and rabbit IgG formed four discrete complexes that sedimented at approximately 7, 10, 13, and 15S. The putative complexes were visible by electron microscopy and appeared to contain one, two, three, and approximately five molecules of IgG. Probably because of its elongated shape, SpA was not clearly visible in these mixtures or in control preparations of SpA alone. Both native IgG and IgG modified by cleavage of its single-hinge disulfide bond formed similar complexes on interaction with SpA. It was possible to resolve heterogeneous mixtures of IgG-SpA complexes by using an analytical ultracentrifuge equipped with a photoelectric scanner interfaced to a small computer. The relative concentrations and sedimentation velocities of different complexes in a mixture were determined from computer-generated integral and derivative plots. Both hydrodynamic and electron microscopic methods revealed that the distribution of complexes was sensitive to the IgG to SpA molar ratio. The relative amounts of faster complexes increased as the IgG to SpA molar ratio was increased. Surprisingly, when the IgG to SpA molar ratio was greater than or equal to 2, the complexes were converted into a unique 17S complex. This rather unprecedented transformation was reversible: the addition of excess SpA caused the dissociation of the 17S complex into a mixture of the 7, 10, 13, and 15S structures. The average translational diffusion coefficient of the 17S complex was 2.62 +/- 0.13 Ficks. In the electron microscope, the complex appeared to be exceptionally compact with an average diameter of 287 A. The stoichiometry of the 17S complex, together with sedimentation equilibrium, diffusion, and electron microscopic measurements, indicated that it is composed of four molecules of IgG and two molecules of SpA.

Conformation and restricted segmental flexibility of C1, the first component of human complement

Seventy selected images of chemically crosslinked C1 are analyzed to illustrate structural details of the C1qC1r2C1s2 complex. From inspection of these images, the C1r2C1s2 tetramer can be seen to be located in the region of the C1q arms, cleanly separated from the C1q heads and from at least 90%, if not all, of the C1q stem. From measurements made upon 65 images, the semicone angles formed between the spreading arms and the symmetry axis passing through the stem of C1 may be calculated. Unlike C1q, for which a wide variety of angles is found, the C1 complex appears to possess a restricted range of angular flexibility with an average value of about 50 degrees. The volume inside the cone formed by the spreading arms of C1q is too small to contain the entire C1r2C1s2 tetramer; at least some of the tetramer must lie outside the cone when it is bound to C1q to form C1. From our knowledge of the sizes and structures of its subunits, and from symmetry considerations, a model is proposed for the configuration of the C1 complex in which the middle portion of the C1r2C1s2 tetramer is centrally located among the arms close to the stem of the C1q and with the two protruding ends of the tetramer wrapped around the outside of the cone. Functional implications of this more rigid structure are discussed with relevance to C1q-induced aggregation of latex beads and C1-induced disaggregation.

Monoclonal autoantibody directed toward histone and capable of inducing LE cell formation

LE cell formation is one feature of systemic lupus erythematosus exhibited by virtually all mice of the NZB/NZW strain and is the result of accumulation of antibodies directed against components of cell nuclei. A hybrid cell line which produces antibodies capable of inducing LE cell formation in vitro has been isolated in a hybridoma fusion using the splenocytes of unimmunized NZB/NZW mice. These monoclonal autoantibodies provide an intense staining of the chromatin in cells of a number of divergent species and tissues. They bind strongly to the histone rich (2 M NaCl) fraction of extracted, isolated nuclei. Further analyses using the antibodies in immune precipitations and in antibody labeling of capillary blots on nitrocellulose sheets of calf thymus histone demonstrate that the antibodies are directed against histones and are capable of reacting with H1, H2a, H2b, H3, and H4 histones individually. In contrast to human autoantibodies with histone specificity, no cross-reactivity of this monoclonal autoantibody with the lymphocyte surface could be detected by either immunofluorescence or immunoelectron microscopy.

Characterization of unusual intermediate density lipoproteins

We report on the physicochemical properties of unusual lipoproteins isolated from both lymph and blood of ruminating cattle. The densities of most of these particles fall within the range between 1.006 and 1.020 g/ml, although densities of 0.97-0.99 g/ml are calculated from chemical composition, assuming a liquid core. The triglycerides of these particles have a high content of saturated fatty acids. The major apoprotein has a mobility on polyacrylamide-SDS gels consistent with a molecular weight of 40,000. The negatively-stained particles appear flattened and asymmetric in electron micrographs. The particles are very large, with molecular weights in the 20 to 250 million dalton range, and they scatter light strongly. The hydrodynamic frictional ratio is about 1.4, consistent with oblate ellipsoids with axial ratios of about 8 to 1. The flat appearance, asymmetric shape, and anomalous densities of the particles would be explained if these lipoproteins consisted of a core of crystallized triglycerides encapsulated within a phospholipid monolayer. Crystallization of the saturated triglycerides could occur during routine lipoprotein isolation, in which temperatures much lower than the melting points of their core lipids are employed. when protocols are done entirely at 37 degrees C, the unusual structures are not observed in the intermediate density class. Although the saturated fats in these bovine lipoproteins are derived from ruminal fermentation, we feel that any triglyceride-rich lipoprotein highly enriched in saturated fats will behave similarly if isolation temperatures are well below the melting points of the core lipids.

Ultrastructure of the first component of human complement: electron microscopy of the crosslinked complex

Electron micrographs are shown of the first component of human complement (C1) which has been crosslinked with a water-soluble carbodiimide to prevent dissociation into its C1q and C1r2C1s2 subunits. Two projections of the crosslinked molecule are seen in the electron micrographs, which are called "top" and "profile." In both views, the C1q heads are visible. From the top, the C1r2C1s2 tetrameric subunits appears to be located centrally on the C1q and folded to form a compact mass obscuring most of the arms and central bundle. In profile, the tetramer appears to be located in the region of the arms between the C1q heads and the central bundle. Both the heads and the rod-like central bundle appear to be free of C1r2C1s2 in these profile projections. Sometimes it is possible to count more than six domains in the region of the C1q heads, as though a portion of the tetramer had unfolded to protrude among the heads.

Characterization of responding cells in oxidative mitogen stimulation. I. Ia+ cells and Ly-1+2+ cells are required for the proliferative response

Addition of anti-Ia sera to cultures of mouse spleen cells stimulated with oxidative mitogens, neuraminidase/galactose oxidase (NaGO) or sodium periodate (NaIO4), inhibits the subsequent proliferative response 30 to 70%. Anti-H-2K or D sera were not specifically inhibitory. Similar inhibition was seen when cells were pretreated with anti-Ia sera and washed before exposure to the mitogenic enzymes. Treatment with anti-Ia serum and complement depletes greater than 89% of the NaGO and the NaIO4 responses but 2% or less of the phytohemagglutinin (PHA) response. The response to NaGO was sensitive to depletion with anti-Thy-1 serum, rabbit anti-mouse brain serum, anti-Ly-1, or anti-Ly-2 serum. Mixtures of Ly-1 and Ly-2-depleted populations did not restore responsiveness. Thus both an Ia+ cell and an Ly-1+2+ T cell are required for [3H]TdR incorporation in response to NaGO treatment.

Characterization of responding cells in oxidative mitogen stimulation. I. Ia+ cells and Ly-1+2+ cells are required for the proliferative response

Addition of anti-Ia sera to cultures of mouse spleen cells stimulated with oxidative mitogens, neuraminidase/galactose oxidase (NaGO) or sodium periodate (NaIO4), inhibits the subsequent proliferative response 30 to 70%. Anti-H-2K or D sera were not specifically inhibitory. Similar inhibition was seen when cells were pretreated with anti-Ia sera and washed before exposure to the mitogenic enzymes. Treatment with anti-Ia serum and complement depletes greater than 89% of the NaGO and the NaIO4 responses but 2% or less of the phytohemagglutinin (PHA) response. The response to NaGO was sensitive to depletion with anti-Thy-1 serum, rabbit anti-mouse brain serum, anti-Ly-1, or anti-Ly-2 serum. Mixtures of Ly-1 and Ly-2-depleted populations did not restore responsiveness. Thus both an Ia+ cell and an Ly-1+2+ T cell are required for [3H]TdR incorporation in response to NaGO treatment.

Characterization of responding cells in oxidative mitogen stimulation. II. Identification of an Ia-bearing adherent accessory cell

Treatment of murine lymph node or spleen cells with anti-Ia serum and complement (C), depletes the subsequent proliferative response of the residual cells to the oxidative mitogen galactose oxidase (NaGO). Restoration of the mitogenic response could be achieved by the addition of adherent accessory cells prepared by a variety of techniques. Loosely adherent dendritic cells were the most efficient population of restoring cells. Treatment of adherent cells with anti-Ia serum and C removed their capacity for restoration. Restoration of the oxidative mitogen response to lymph node cells depeleted of adherent cells by passage over nylon wool and Sephadex columns was similar to restoration of Ia- depleted lymphocyte populations. Further NaGO-induced lymphocyte transformation requires an Ly-1+2+ T lymphocyte and an Ia-positive adherent accessory cell.

Characterization of responding cells in oxidative mitogen stimulation. II. Identification of an Ia-bearing adherent accessory cell

Treatment of murine lymph node or spleen cells with anti-Ia serum and complement (C), depletes the subsequent proliferative response of the residual cells to the oxidative mitogen galactose oxidase (NaGO). Restoration of the mitogenic response could be achieved by the addition of adherent accessory cells prepared by a variety of techniques. Loosely adherent dendritic cells were the most efficient population of restoring cells. Treatment of adherent cells with anti-Ia serum and C removed their capacity for restoration. Restoration of the oxidative mitogen response to lymph node cells depeleted of adherent cells by passage over nylon wool and Sephadex columns was similar to restoration of Ia- depleted lymphocyte populations. Further NaGO-induced lymphocyte transformation requires an Ly-1+2+ T lymphocyte and an Ia-positive adherent accessory cell.

Characterization of responding cells in oxidative mitogen stimulation. III. Presence of I-A- and I-J, E, C-subregion gene products on the surface of required cells

Ia antigens coded by genes of the murine major histocompatibility complex are expressed on the surface of a population of cells critical to the proliferative response of murine spleen cells to the oxidative mitogen neuraminidase/galactose oxidase. By selective depletion with antiserum and complement, Ia antigens coded (or determined) by the I-A and I-J, E, C subregions of the Ir region can be detected on the surface of cells required for the response. In addition, I-A-subregion products have a functional significance in cellular activation which can be demonstrated by blocking experiments with anti-Ia serum in the absence of complement.

Matching manpower with patient care needs: whose decision?

Unlimited and unplanned proliferation of health manpower education and training programs is producing increasingly specialized personnel, without concern for the costs their services generate or for the kinds of services that will be needed as more Americans gain access to care. Only more national planning to relate preparation and expectations of graduates to affordable service needs will prevent frustration, underutilization, and unemployment of all health manpower.

Anion transporters in plant mitochondria

The swelling of potato (Solanum tuberosum L.) mitochondria in isosmotic ammonium salts of phosphate, chloride, malate, succinate, and citrate was investigated by measuring light scattering. Potato mitochondria swell spontaneously in ammonium phosphate, and this swelling can be inhibited in N-ethylmaleimide. They swell in ammonium malate or succinate only after the addition of inorganic phosphate and in ammonium citrate only after the addition of both phosphate and a dicarboxylic acid. Pentylmalonate inhibits swelling in ammonium citrate solutions by competing for dicarboxylate entry. The results indicate that potato mitochondria possess a phosphate-hydroxyl carrier, a dicarboxylate carrier, and a tricarboxylate carrier.

Effects of 2-Butylmalonate, 2-Phenylsuccinate, Benzylmalonate, and p-Iodobenzylmalonate on the Oxidation of Substrates by Mung Bean Mitochondria

The effect of inhibitors of carboxylic acid anion transport on the oxidation of substrates by mung bean (Phaseolus aureus) mitochondria was investigated. The oxidation of malate in the presence of either glutamate or cysteine sulfinate was inhibited by 2-butylmalonate, 2-phenylsuccinate, benzylmalonate, and p-iodobenzylmalonate in both intact and broken mitochondria. The oxidation of succinate, on the other hand, was inhibited in intact but not in broken mitochondria. The oxidation of reduced nicotinamide adenine dinucleotide was inhibited only by p-iodobenzylmalonate. This inhibition occurred only in coupled mitochondria and could be reversed by the addition of adenosine diphosphate.These results suggest that the compounds studied inhibit the entry of succinate and probably also of malate into mung bean mitochondria. All four compounds inhibit the enzyme (s) which oxidize malate while p-iodobenzylmalonate also interferes with oxidative phosphorylation.