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.

Corticotropin releasing factor-like immunoreactivity in the rat brain as revealed by a modified cobalt-glucose oxidase-diaminobenzidine method

A cobalt-glucose-oxidase diaminobenzidine (Co-GOD) method, employing a specific antiserum against rat corticotropin releasing factor (CRF), was applied to determine immunohistochemically a widespread and detailed localization of corticotropin releasing factor-like immunoreactivity (CRFI) in the rat brain. Besides the CRFI cells in the paraventricular hypothalamic nucleus that project to the median eminence, CRFI cells were demonstrated in many brain regions, including the olfactory bulb, cerebral cortex, septal nuclei, hippocampus, amygdala, thalamic nuclei, medial hypothalamic nuclei, lateral hypothalamic area, perifornical area, central gray, cuneiform nucleus, inferior colliculus, raphe nuclei, mesencephalic reticular formation, laterodorsal tegmental nucleus, locus coeruleus, parabrachial nuclei, mesencephalic tract of the trigeminal nerve, pontine reticular formation, lateral superior olive, vestibular nuclei, prepositus hypoglossal nucleus, nucleus of the solitary tract, dorsal motor nucleus of the vagus, lateral reticular nucleus, nucleus of the spinal tract of the trigeminal nerve, external cuneate nucleus, inferior olive, and medullary reticular formation. CRFI-reacting neural processes were also detected in these same areas. In particular, the median eminence, lateral septum, bed nucleus of the stria terminalis, mesencephalic reticular formation, parabrachial nuclei, and nucleus of the solitary tract contained large numbers of CRFI fibres. The widespread localization of CRFI demonstrated in the present study strongly suggests that CRF, like many other neurohormones and peptides, may act as a neurotransmitter and/or neuromodulator in numerous extrahypothalamic circuits, as well as participate in neuroendocrine regulation.

Regulation of integrin alpha 5 beta 1-fibronectin interactions by divalent cations. Evidence for distinct classes of binding sites for Mn2+, Mg2+, and Ca2+

Integrin-ligand interactions are known to be dependent on divalent cations, although the precise role of cations in ligand binding is still unclear. Using the interaction between alpha 5 beta 1 and fibronectin as a model system, we have performed a comprehensive analysis of the effects of Mn2+, Mg2+, and Ca2+ on ligand binding. Each cation had distinct effects on the ligand-binding capacity of alpha 5 beta 1:Mn2+ promoted high levels of ligand binding, Mg2+ promoted low levels of binding, and Ca2+ failed to support binding. Studies of the effects of different combinations of cations on ligand binding indicated that the cation-binding sites within alpha 5 beta 1 are not all identical, or of broad specificity, but instead each site shows a distinct preference for one or more cations. Ca2+ strongly inhibited Mn(2+)-supported ligand binding, but this inhibition was noncompetitive, suggesting that Ca2+ recognizes different cation-binding sites to Mn2+. In contrast, Ca2+ acted as a direct competitive inhibitor of Mg(2+)-supported ligand binding, implying that Ca2+ can displace Mg2+ from the integrin. However, low concentrations of Ca2+ greatly increased the apparent affinity of Mg2+ for its binding site, suggesting the existence of a distinct high affinity Ca(2+)-binding site. Taken together, our results imply that the ligand-binding capacity of alpha 5 beta 1 can be regulated in a complex manner through separate classes of binding sites for Mn2+, Mg2+, and Ca2+.

Molecular and antigenic heterogeneity of the rat leukocyte-common antigen from thymocytes and T and B lymphocytes

The molecular forms and antigenic heterogeneity of the leukocyte-common antigen (L-CA) of rat lymphocytes have been analyzed. Thymocytes show one main band at 180 kDa, T cells four bands at 180, 190, 200 and 220 kDa and B cells one broad band at about 240 kDa. T helper and T cytotoxic cell subsets show the same four bands with some differences in the proportion of each. Four mouse monoclonal antibodies (MRC OX-1, 28, 29 and 30) reacted with all molecular forms of L-CA and fell into two sets that were noncompetitive in binding to L-CA (MRC OX-1, 28, 29 vs. OX-30). The antigenic determinants seen by all these antibodies were lost when L-CA was reduced and alkylated. Three antibodies (MRC OX-22, 31 and 32) reacted selectively with B cells, T cytotoxic cells and about 2/3 of T helper cells. OX-22 and OX-31 competed for binding but were noncompetitive with OX-32. All these antibodies bound to a subfraction of the 190, 200 and 220-kDa forms of T cell L-CA but not at all to the 180-kDa form of T cells or thymocytes. One antibody bound to B cells only (MRC OX-33) and precipitated a subfraction of B cell L-CA. With all the antibodies that did not label thymocytes the antigenic determinants survived reduction and alkylation. Subsequent proteolysis with trypsin then destroyed all determinants except the one reacting with MRC OX-22 antibody. In this case tryptic peptides retained full antigenic activity which was, however, destroyed by further proteolysis with pronase.

T-lymphocyte heterogeneity in the rat: separation of functional subpopulations using a monoclonal antibody

W3/25 antibody is the monoclonal product of a hybrid cell resulting from the fusion of a mouse myeloma cell line with spleen cells from a mouse immunized with rat thymocytes. Pure clones have been derived, and segregants free of parental myeloma chains have been isolated. Previous studies have shown that this antibody recognizes a subpopulation of T cells among rat thoracic duct lymphocytes. In the work reported here, three T-cell functions were assayed after separating rat thoracic duct lymphocytes on the fluorescence-activated cell sorter on the basis of labeling with W3/25 antibody. Two of the functional activities appeared to be completely segregated by this procedure. Thus, helper cell activity for an anti-hapten plaque-forming cell response was confined to the labeled population, whereas the allogeneic suppressive effect produced in a parental vector F1 adoptive transfer was mediated by cells in the unlabeled fraction. The third function, graft-versus-host activity, was almost entirely contained within the labeled subpopulation. It is concluded that the antigenic determinant recognized by the monoclonal antibody W3/25 is a differentiation marker for T-cell functional subpopulations.

Non-producer human cells induced by murine sarcoma virus

Non-produces (NP) human cells were isolated from transformed foci induced by the Kirsten mouse sarcoma virus. These morphologically altered NP cells produced neither infectious virus nor complement-fixing antigens of the murine sarcoma-leukemia virus complex. However, the sarcoma virus genome could be rescued from these NF cells by co-cultivation with cells carrying "helper" Kirsten mouse leukemia virus or Woolly Monkey leukemia virus. The possible usefulness of these cells in efforts designed to detect covert or repressed RNA tumor viruses in various animal and human tissues is discussed.

Parasagittal organization of the rat cerebellar cortex: direct correlation between antigenic Purkinje cell bands revealed by mabQ113 and the organization of the olivocerebellar projection

The Purkinje cells of the cerebellar cortex and the cortical afferent and efferent projections are organized into parallel parasagittal zones. The parasagittal organization is clearly revealed by immunocytochemistry with a monoclonal antibody, mabQ113. The mabQ113 antigen is confined to a subset of Purkinje cells that are clustered together to form an elaborate, highly reproducible pattern of bands and patches, interspersed with similar mabQ113- regions. The mabQ113+ territories have been classified into seven parasagittal bands (P1+-P7+) in each hemicerebellum. The degree of correspondence between the compartments revealed by the anterograde labeling of the olivocerebellar projection and by mabQ113 immunocytochemistry has been explored in the adult rat. Horseradish peroxide-wheat germ agglutinin conjugate was injected as an anterograde tracer into the inferior olivary complex. When the injection site did not encompass all the olive, an incomplete, patchy labeling of the molecular layer was seen in the cerebellar cortex. Labeled zones of the molecular layer were interrupted by unlabeled regions to give a pattern of parasagittal cortical bands. The positions of these bands were compared with the distribution of the mabQ113+ antigenic bands as seen on the two adjacent sections. Labeled climbing fibers were found to terminate on both mabQ113+ and mabQ113- Purkinje cell zones. The mabQ113+/mabQ113- boundaries and the bands of climbing fibers seen by using the anterograde tracer typically coincide. The one consistent exception is the midline band of mabQ113+ Purkinje cells, P1+. The normal olivocerebellar projection is exclusively contralateral and the climbing fiber projection to the paramedian vermis splits P1+ down the middle, implying that it consists of two adjacent mabQ113+ bands not separated by mabQ113-territory. It is likely that the climbing fiber projection to the cerebellar cortex and the distribution of the two Purkinje cell phenotypes share a common compartmental organization.

Rabbit monoclonal antibodies: generating a fusion partner to produce rabbit-rabbit hybridomas

During the last 15 years several laboratories have attempted to generate rabbit monoclonal antibodies, mainly because rabbits recognize antigens and epitopes that are not immunogenic in mice or rats, two species from which monoclonal antibodies are usually generated. Monoclonal antibodies from rabbits could not be generated, however, because a plasmacytoma fusion partner was not available. To obtain a rabbit plasmacytoma cell line that could be used as a fusion partner we generated transgenic rabbits carrying two transgenes, c-myc and v-abl. These rabbits developed plasmacytomas, and we obtained several plasmacytoma cell lines from which we isolated hypoxanthine/aminopterin/thymidine-sensitive clones. One of these clones, when fused with spleen cells of immunized rabbits, produced stable hybridomas that secreted antibodies specific for the immunogen. The hybridomas can be cloned and propagated in nude mice, and they can be frozen without change in their ability to secrete specific monoclonal antibodies. These rabbit-rabbit hybridomas will be useful not only for production of monoclonal antibodies but also for studies of immunoglobulin gene rearrangements and isotype switching.

Characterization of allergen-induced bronchial hyperresponsiveness and airway inflammation in actively sensitized brown-Norway rats

Bronchial responsiveness to inhaled acetylcholine (ACh) and inflammatory cell recruitment in bronchoalveolar lavage fluid (BALF) were studied in inbred Brown-Norway rats actively sensitized to, and later exposed to, ovalbumin (OA). We examined animals 21 days after initial sensitization at 18 to 24 hours, or 5 days after a single challenge, or after the last of seven repeated exposures administered every 3 days. BALF was examined as an index of inflammatory changes within the lung. Animals repeatedly exposed to OA aerosols had an increased baseline lung resistance and a significant increase in bronchial responsiveness to inhaled ACh compared to control animals at both 18 to 24 hours and 5 days after the last OA exposure. Sensitized animals receiving a single OA aerosol also demonstrated bronchial hyperresponsiveness (BHR) to inhaled ACh (p less than 0.01) at 18 to 24 hours of a similar order as the multiple-exposed group. There was a significant increase in eosinophils, lymphocytes, and neutrophils in BALF at 18 to 24 hours but not at 5 days after single or multiple exposure to OA aerosol in the sensitized groups. Control animals demonstrated no changes in bronchial responsiveness, although a small but significant increase in inflammatory cells was observed compared to saline-only treated animals. There was a significant correlation between bronchial responsiveness and eosinophil counts in the BALF in the single allergen-exposed group (Rs = 0.68; p less than 0.05). We conclude that (1) BHR after allergen exposure in sensitized rats is associated with the presence of pulmonary inflammation but persists despite the regression of inflammatory cells in BALF after multiple OA exposures, and (2) this rat model has many characteristics of human allergen-induced BHR.

Airborne allergens associated with asthma: particle sizes carrying dust mite and rat allergens measured with a cascade impactor

Patients with asthma may develop acute symptoms after exposure to domestic or laboratory animal allergens; however, they are usually not aware of a direct relationship between their acute attacks and exposure to pollen or dust mite allergens. The present experiments were designed to study whether the differences in symptoms could be explained by differences in the number or size of particles carrying airborne allergens. Airborne particles were collected with a filter or on the stages of a cascade impactor, and allergens were measured by use of inhibition radioimmunoassays. In rat rooms and during disturbance of rat litter, a large proportion of rat urinary allergen (45.9%) was collected on the second stage of the impactor (mean size approximately 7 microns diameter). When sampled 15 to 35 minutes after disturbance, 16% of these medium-sized particles were still airborne. By contrast, during disturbance of house dust, a significantly larger proportion of dust mite, antigen P1 (80.6 +/- 11.8%; p less than 0.001) was collected on the first stage of the impactor, and in keeping with the apparent size of these particles (diameter greater than 10 microns), very little of this allergen (less than 4%) was still airborne when sampled 15 to 35 minutes after disturbance. With nebulized diluted rat urine, approximately 75% of the allergen was collected on the fourth and final stages of the cascade impactor in keeping with the expected size, 0.5 to 3 microns in diameter. These results demonstrate that natural exposure to both allergens is strikingly different from the conditions used for bronchial provocation.(ABSTRACT TRUNCATED AT 250 WORDS)

Preventive effect of monoclonal anti-L3T4 antibody on development of diabetes in NOD mice

We analyzed the surface phenotypes of infiltrated cells in pancreases of nonobese diabetic (NOD) mice with monoclonal antibodies to mouse lymphocytes. Most of the infiltrated cells were Thy1+ and Ly1+ T-lymphocytes, and most of them were L3T4+ helper T-lymphocyte subsets. To elucidate the role of L3T4+ T-lymphocytes in the development of insulitis and diabetes in NOD mice, we treated the animals with injections of monoclonal anti-L3T4 antibody. Administration of this antibody prevented the insulitis and diabetes in NOD mice. These results lead to conclusions that the L3T4+ helper T-lymphocytes may play an essential role in the pathogenesis of type I diabetes and that the manipulation of the OKT4+ (Leu3+) T-lymphocyte subset, the human homology of L3T4, with monoclonal antibodies may provide effective therapy for human type I diabetes.

Autogenous immunity to endogenous RNA tumor virus. Radioimmune precipitation assay of mouse serum antibody levels

The radioimmune precipitation assay using (3)H-labeled AKR leukemia virus was applied to the detection and quantitation of natural serum antibodies directed against endogenous murine leukemia virus (MuLV) envelope antigens B6C3F(1) and BALB/c mice, which have low natural incidences of leukemia and lymphoma, and AKR mice, which have a high incidence, were used in this study. Sera from mice of various age groups were assayed. A marked difference in age-associated levels of the autogenous immune response to endogenous murine leukemia virus was detected, and the quantitative differences among these strains were inversely related to the incidence of lymphoma. The radioimmune precipitation test as applied was 500 times more sensitive than virus neutralization. That the reactions we have observed are specific is suggested by several lines of evidence, including the nonreactivity of normal hamster and absorbed rat serum, the positive reaction of absorbed rat anti-AKR serum, the inhibition of precipitation of labeled virus by purified unlabeled virus, and isopycnic gradient analysis of the reactive products.

The distribution, ultrastructure, and chemistry of microfilaments in cultured chick embryo fibroblasts

The distribution, ultrastructure, and chemistry of microfilaments in cultured chick embryo fibroblasts were studied by thin sectioning of flat-embedded untreated and glycerol-extracted cells, histochemical and immunological electron microscopic procedures, and the negative staining of cells cultured on electron microscopic grids. In these cultured cells, the microfilaments are arranged into thick bundles that are disposed longitudinally and in looser arrangements in the fusiform-shaped cells. In the latter case, they are concentrated along the margins of the flattened cell, on the dorsal surface, and particularly at the ends of the cell and its ventral surface, where contact is made with the plastic dish or with other cells. Extracellular filaments, presumably originating from within the cell, are found at these points of contact. The microfilaments are composed in part of an actin-like protein. These filaments are between 70 and 90 A in diameter, they are stable in 50% glycerol, they have an endogenous ATPase (myosin-like?) associated with them, they bind rabbit muscle heavy meromyosin, and they specifically bind antibody directed against isolated actin-like protein. In the cultured chick embryo fibroblasts, the microfilaments are essential for the establishment and maintenance of form, and they are probably critical elements for adhesion and motility. The microfilaments might also serve as stabilizers of intramembranous particle fluidity.

The release of spasmogenic substances from human chopped lung tissue and its inhibition

1. Human lung tissue, passively sensitized with reaginic antibodies, released prostaglandins E(1), E(2) and F(2alpha) in addition to histamine and slow reacting substance (SRS-A), when exposed to the appropriate antigen. No rabbit aorta contracting substance (RCS) was detected.2. Experiments with rats and guinea-pigs showed that the release of RCS is not confined to anaphylactic reactions mediated by non-reaginic antibodies but may be a feature of anaphylaxis in guinea-pigs alone.3. Human lung tissue gently agitated with a blunt nylon rod liberated an E-type prostaglandin and RCS in addition to histamine and SRS-A.4. Human isolated bronchial muscle was contracted by RCS.5. Disodium cromoglycate antagonized the release of prostaglandins during anaphylaxis but not during agitation of human lung tissue, whereas indomethacin blocked the release of prostaglandins during agitation and anaphylaxis.6. The release of an E-type prostaglandin during anaphylaxis in human lung tissue, which inhibits the further release of histamine could be another example of the regulatory role of prostaglandins in body functions.

Cloning and expression of the chromosomal immune interferon gene of the rat

The chromosomal immune interferon gene of the rat (IFN-gamma) was identified by screening a recombinant rat lambda phage library with a human IFN-gamma cDNA probe. In contrast to the genes of other rat IFNs, this rat IFN-gamma chromosomal gene contains introns and its structural organization closely resembles that of the human and murine IFN-gamma genes. The rat IFN-gamma gene encodes a signal sequence of 19 amino acids followed by the mature IFN-gamma protein of 137 amino acids. The gene was expressed under control of the simian virus 40 (SV40) early promoter in Chinese hamster ovary (CHO) cells deficient in dihydrofolate reductase (DHFR) after co-transformation with a plasmid containing the mouse DHFR gene. Initial transformants with a DHFR+ phenotype produced IFN-gamma titres ranging from 20 to 1600 units/ml. After stepwise increases in the concentration of methotrexate (MTX) in the growth medium of transformed CHO cells, MTX-resistant clones producing 80 000-100 000 units per ml were isolated. Protein analysis of supernatants of these MTX-resistant cells by polyacrylamide gel electrophoresis revealed a product with an apparent mol. wt. of 18 000 daltons which was not detectable in the growth medium of DHFR+ transformants that did not produce IFN. The product was identified as rat IFN-gamma and constituted approximately 5% of the proteins excreted from these cells.

Allergen exposure, atopy and smoking as determinants of allergy to rats in a cohort of laboratory employees

This study aimed to examine the relationship between exposure to rat urinary allergens, atopic status, smoking and the development of allergic symptoms and specific sensitization. It is a case-referent analysis of a cohort of 342 newly employed laboratory animal workers. Cases comprised persons developing symptoms of laboratory animal allergy or a positive skin prick test to rat urinary allergens; each was matched with up to two asymptomatic referents. Subjects were assigned to categories of exposure based on measurements of airborne rat urinary allergens. Of the cases, 80% reported that their symptoms started within 2 yrs of employment. The odds ratio (OR) for development of each symptom type (respiratory, eye or nose and skin) and of an immediate skin test reaction was increased in those with direct contact with rats. A gradient of increasing OR for the development of any such symptom across exposure categories was found; for respiratory symptoms and skin test reactions the OR for subjects in the highest exposure category were lower than those in intermediate categories, a pattern attenuated when the analysis was confined to outcomes developing within 2 yrs of first exposure. Atopy increased the OR of most outcomes as did cigarette smoking, although there was no evidence of a relationship between smoking and the development of a specific skin test reaction. In conclusion, allergen exposure was confirmed as the most important determinant of laboratory animal allergy; by implication, measures to reduce exposure may be the most effective means to reduce its incidence.

Heterogeneity of macrophages in the rat evidenced by variability in determinants: two new anti-rat macrophage antibodies against a heterodimer of 160 and 95 kd (CD11/CD18)

A set of three monoclonal antibodies (MoAbs), ED1, ED2, and ED3, has been shown to recognize in situ different subsets of macrophages in the rat. This macrophage diversity can be correlated with differences in stage of differentiation of cells belonging to one lineage. The present study quantifies this antigen distribution in the macrophage fractions of several lymphoid organs provided by Percoll centrifugation. Four new MoAbs (ED4, ED7, ED8, and ED9) raised against macrophages are included in this study. The tissue distribution of each of the four new MoAbs is determined by immuno- and enzyme-histochemistry on cryostat sections. The MoAbs recognize distinct subpopulations of macrophages. The new MoAbs ED4, ED7, ED8, and ED9 recognize granulocytes and other unrelated cell types, as well as cells of the mononuclear phagocyte system. ED7 and ED8 recognize a surface heterodimer of Mr 160,000 and 95,000.

Quantitative assessments of IgG and IgE antibodies to inhalant allergens in patients with atopic dermatitis

Using antigen-binding radioimmunoassays, we have measured class specific antibodies against two major inhalant allergens, antigen P1 from D. pteronyssinus and Rye I from grass pollen, in sera from 69 patients with atopic dermatitis. The results show that many of the patients have IgE ab to these allergens in keeping with their skin tests. In all cases, the IgE ab was paralleled by IgG ab to the same allergen. In many sera, IgE ab to these inhalant allergens made a significant contribution to the total serum IgE. With two other allergens to which these patients had not been exposed, specific IgE ab was detected in only one serum, whereas the 42 sera tested did not contain IgE ab to diphtheria toxin. Eleven of the adult patients with atopic dermatitis had no history of asthma and had strongly positive skin tests. This group of patients had levels of total IgE and specific ab to antigen P1 that were very similar to those found in a comparable group of patients who had both atopic dermatitis and asthma. Our recent finding that allergens applied to the skin can induce delayed eczematous lesions provides a mechanism by which allergens could contribute to skin lesions. Our present results support the view that specific sensitivity to common allergens should be taken into account in considering the causes of these patients' skin lesions.