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S R Webb

Publications and source records attributed to S R Webb.

At least 55 records · Page 3Linked to original sources
PubMed1988

Analysis of T hybridomas prepared from a T cell clone with three specificities. Recognition of self + X and allo-H-2 determinants segregates from recognition of Mlsa determinants.

To see k information on T cell recognition of Mlsa determinants, hybridomas were prepared from a well-characterized F23.2+ (V beta 8.2+) T cell clone specific for three different ligands, i.e., 1) Mlsa determinants, 2) fowl gamma-globulin (F gamma G) plus self-H-2 (H-2d), and 3) allo-H-2, e.g., H-2p, determinants. Fusion of the clone to the BW5147 thymoma line produced a triple-reactive T hybridoma which generated two types of spontaneous variants. One type of variant (type I) lost Mlsa reactivity but retained reactivity to both F gamma G/H-2d and allo-H-2p. These variants, which were generated at high frequency, stained strongly with a mAb, A1.57, with idiotypic specificity for the TCR molecules of the parental clone. The second type of variant (type II) reacted to Mlsa determinants but showed no reactivity to F gamma G/H-2d or to allo-H-2p. These variants failed to express the A1.57 idiotypic determinants of the parent clone, but were F23.2+ (V beta 8.2+); nonequilibrium pH gradient electrophoresis analysis suggested that these hybrids expressed a mixed TCR heterodimer composed of the parental clone beta-chain and the BW5147 alpha-chain. Three aspects of the data are very difficult to accommodate with the view that Mlsa, F gamma G, and allo-H-2 determinants are all recognized via a common TCR molecule: 1) the independent (and frequent) segregation of Mlsa reactivity from F gamma G/H-2d and allo-H-2p reactivity, 2) the retention of Mlsa reactivity by the type II variants despite loss of the parental clone alpha-chain, and 3) the loss of Mlsa reactivity by the type I variants despite high expression of the A1.57+ TcR molecules derived from the parental clone. The data support a model in which Mlsa determinants are recognized by a separate T cell structure, which we envisage as a monomorphic accessory molecule unrelated to the TCR. Since the type II hybridoma variants invariably retained quantitatively normal TcR expression, the triggering phase of anti-Mlsa responses appears to be TCR dependent. The model we favor is that anti-Mlsa/Mlsa interaction increases TCR binding with Ia epitopes to above the threshold required for cell triggering. A key feature of this model is that Mlsa and Ia determinants are recognized as separate structures rather than as a complex.

Animals↗
PubMed1988

The functional significance of the sympathetic innervation of mucous glands in the bronchi of man.

1. Pieces of human bronchi, from lung resected for carcinoma of the bronchus, were mounted in Ussing chambers and given [35S]sulphate as radiolabelled precursor of mucous glycoproteins (mucins). The release of 35S, bound to macromolecules, into the luminal half-chamber was used as an index of mucin secretion. 2. Noradrenaline, at concentrations of 1, 10 and 100 microM, was given into both halves of the Ussing chamber. At the lowest concentration, noradrenaline failed to change mucin output, but at the two higher concentrations it stimulated output. 3. In other experiments the sympathetic nerves in the bronchial wall were labelled with 5-hydroxydopamine and examined under the electron microscope. The distances between adrenergic nerve varicosities and submucosal glands were measured; some sympathetic nerve varicosities were seen within 1 microns of gland cells. 4. A simple mathematical model for the diffusion of noradrenaline was used to predict the concentrations of the transmitter likely to result at different distances from a nerve if one or more vesicles of noradrenaline were released. 5. The model predicts that the release of a single large vesicle of noradrenaline is likely to generate an effective concentration of transmitter provided that the nerve is within 1 micron of the target cell.

Bronchi↗
PubMed1988

T-cell selection in the thymus.

Differentiation of early thymocytes into mature T cells depends upon intrathymic T cell contact with major histocompatibility complex (MHC) molecules, i.e., H-2 molecules in mice. T cell recognition of H-2 molecules in the thymus has two consequences. First, some T cells undergo a process of positive selection which leads specifically-reactive immature thymocytes to survive and differentiate into mature functional T cells. Second, T cells with high affinity for H-2 molecules undergo negative selection (tolerance). We and others have argued that positive selection is controlled by thymic epithelial cells, especially cortical epithelium, whereas negative selection reflects contact with bone-marrow (BM) derived cells. This scheme appears to be an oversimplication because we have recently found evidence that a non-BM-derived component of the thymus, presumably epithelial cells, is highly tolerogenic for CD4+ cells. Whether tolerance of CD4+ cells is controlled by cortical epithelium or medullary epithelium is unclear. In this respect it is of interest that chronic injection of mice with cyclosporine A results in selective destruction of medullary epithelial cells and impaired induction of self tolerance.

Animals↗
PubMed1986

Neutralization epitope diversity of coxsackievirus B4 isolates detected by monoclonal antibodies.

Only recently have we begun to fully realize the diversity of virions within a single human isolate of the group B Coxsackieviruses. These intratypic (strain) differences may be one of the important factors influencing pathogenesis, e.g., myocarditis vs. pancreatitis. Yet, until the virion strains within a type can be well differentiated, a thorough analysis of the pathogenic potential of each is not possible. We compared two human isolates, JVB and Edwards, and 15 isolates derived from these two in search of determinants of strain specificity and to evaluate the diversity/stability of neutralization epitopes on the virions comprising each isolate. Polyclonal antisera failed to show strain specific determinants. However, monoclonal antibodies directed to individual neutralization epitopes defined strain specific differences. Plaque reduction neutralization tests with these monoclonal antibodies allowed the quantitation of the expression of epitopes on the virions in each isolate. These data helped to establish the limits of diversity and stability of the neutralization epitopes of Coxsackievirus B4 virions and describe the changes in epitopes among laboratory isolates.

Antibodies, Monoclonal↗
PubMed1986

Coxsackievirus B4 heterogeneity: effect of passage on neutralization and mortality.

We have compared two CB4 isolates for virulence, tissue tropism, and antigenic drift using monoclonal antibodies. Both isolates replicated in C57B1/6 and Balb/c mice. The human isolate Edwards, recovered from a fatal case of encephalohepatomyocarditis, produced lethal infection in adult animals. Lethal infections were associated with high viral titers in visceral organs but not with the presence of specific neutralizing epitopes. Virulence seemed stable upon passage, and also the avirulent JVB isolate retained its phenotype. Mock infection and recovery experiments demonstrated the stability of these characteristics. Neither the tissue from which the virus was isolated nor the cell line used in isolation significantly reduced virulence. However, antigenic variation among isolates was abundant. Thus, the set of monoclonal antibodies employed here may not be appropriate positive markers for virulence. This study suggests that CB4 virulence is stable upon extended in vitro passage and limited in vivo passage and that isolation site and method may not select for or against virulence. It is therefore possible that laboratory adapted strains of CB4, although antigenically different from freshly isolated specimens, may still retain these properties responsible for virulence present in low passage isolates and may be, with regard to virulence, very similar to freshly isolated specimens.

Animals↗
PubMed1985

T cell receptors for responses to Mls determinants and allo-H-2 determinants appear to be encoded on different chromosomes.

Previous studies have shown that T cell clones specific for strong Mlsa,d determinants concomitantly display apparently random reactivity to allo-H-2 determinants. One explanation for this finding is that T cell recognition of Mlsa,d and allo-H-2 determinants is controlled by separate sets of receptors. If these receptors were chromosomally unlinked, karyotypically unstable T cell hybrids with dual reactivity for Mlsa,d and particular allo-H-2 determinants would be expected, occasionally, to lose reactivity for one set of determinants, but not the other. The results presented here provide direct support for this prediction.

Animals↗
PubMed1985

Capacity of small B cell-enriched populations to stimulate mixed lymphocyte reactions: marked differences between irradiated vs. mitomycin C-treated stimulators.

To investigate whether small B cells can stimulate mixed lymphocyte reactions (MLR), highly purified populations of large vs. small B cell fractions were tested for their capacity to evoke MLR across Mls vs. H-2 barriers. Large B cell fractions stimulated high MLR to Mls and H-2 determinants, irrespective of whether the stimulators were exposed to irradiation or pretreated with mitomycin C. In accord with the findings of others, irradiated small B cell fractions proved to be very poor stimulators of MLR. Significantly, however, mitomycin C-treated small B cell fractions elicited high MLR, particularly to Mls determinants. The finding that small B cell fractions treated with irradiation are poor stimulators of T cells correlates with the known radiosensitivity of B cells. In this respect, the widely held view that small B cells do not have antigen-presenting cell (APC) function rests largely on studies with irradiated B cells. The present finding that T cells respond well to small B cells treated with mitomycin C, however, indicates that small B cell fractions do have APC function. Whether the APC function of small B cells reflects a response to resting B cells per se rather than to cells undergoing activation in vitro, however, remains to be ascertained.

Animals↗
PubMed1985

Physiology of B cells in mice with X-linked immunodeficiency. I. Size, migratory properties, and turnover of the B cell pool.

In terms of certain immune functions and density of surface IgM, B cells from xid mice are often viewed as the equivalent of the immature (Lyb-5-) B cell subset of normal adult mice. In this paper we examine xid B cells with regard to certain physiologic functions, including homing to the lymphoid tissues, recirculation, and turnover. Xid mice were found to possess about one-third of the total number of B cells found in normal mice. This applied irrespective of whether one examined the spleen, lymph nodes, or outputs of B cells in thoracic duct lymph. In terms of migration to spleen, lymph nodes, and Peyer's patches, capacity to recirculate from blood to thoracic duct lymph, and turnover, xid B cells proved to be indistinguishable from normal spleen or thoracic duct B cells. Within these parameters, most xid B cells closely resemble the normal mature long-lived population of B cells residing in the recirculating pool of normal mice. Because xid B cells are functionally quite different from normal mature B cells, it seems reasonable to view xid B cells as an abnormal population not represented in normal mice.

Animals↗
PubMed1984

Negative selection in vivo reveals expression of strong Mls determinants in mice with X-linked immunodeficiency.

Evidence is presented that mice with X-linked immunodeficiency (xid) express strong Mlsa,d determinants, a putative marker of the mature subset of B cells. Although young (3-5 wk) (CBA/N X DBA/2)F1 male (xid+) mice stimulated only very weak mixed lymphocyte reactions (MLR) to Mlsa,d determinants, older mice (greater than 7 wk) regularly elicited conspicuous responses, despite being totally unresponsive to TNP-Ficoll. Expression of Mlsa,d determinants by xid+ mice was also detected by the procedure of negative selection in vivo. Thus BALB/c T cells were totally depleted of Mlsa,d reactivity after blood to lymph recirculation through 10-wk old irradiated xid+ (CBA/N X DBA/2)1 male mice. Significantly, a marked (90%) reduction in the anti-Mlsa,d response also occurred with T cell filtration through 3-wk xid+ mice, i.e., mice that elicit only minimal primary MLR; filtration through 3-wk xid- normal female mice led to near-complete (99%) negative selection. Collectively these data indicate either, (a) that xid+ mice contain appreciable numbers of cells with at least some of the properties of mature B cells, or (b) that the expression of Mlsa,d determinants is not restricted to mature B cells. In either case, B cells from xid mice cannot be viewed as a simple model for immature normal B cells.

Aging↗
PubMed1983

Diversity within a human isolate of coxsackie B4: relationship to viral-induced diabetes.

The ability of different strains of a single virus type to produce different pathogenic expressions is well documented within the picornavirus group. Coxsackievirus, group B, type 4 (CB4) has been associated with viral-induced diabetes in man, but expression of its potential to induce diabetes in experimental animals is variable. Evidence is presented here for one of the primary sources of this variability that could explain resulting contradictory reports offered in support or rejection of its diabetogenic potential. C57B1/6 and SWR mice were infected with the Edwards isolate of CB4 (CB4-Edw) and three of its plaque-purified virion "strains." These were designated Edwards isolate-1 (E1), E2, and E3. CB4-Edw, E1, E2, and E3 were serologically similar by infectivity neutralization tests, had identical plaque morphology, and replicated to a similar level in the pancreas. The most profound difference was the level of virus antigen accumulation in the islet cells as determined by immunoperoxidase localization. CB4-Edw had moderate antigen accumulation in most islet cells of SWR mice but was restricted to only a few specific cells within the periphery islets of C57B1/6 mice. Unlike CB4-Edw all three new isolates accumulated antigen in most islet cells of both mouse strains. Virus isolate (strain) E2 showed the most intense accumulation in islet cells. These observations suggest that the Edwards isolate of CB4, like other human isolates of CB4 virus, probably exists as a heterogeneous population of virion strains. The pathogenic consequences and expression of any diabetogenic potential is, therefore, dependent on virus strain selection. This diversity must be considered when evaluating the pathogenic nature of CB4 viruses in experimental animals and the possible role of the viruses in diabetes of man.

Animals↗
PubMed1983

Heterogeneity of a human isolate of Coxsackie B4: biological differences.

Evidence is presented to demonstrate existence of virion heterogeneity within the human isolate, Edwards, of Coxsackievirus B4 (CB4-Edw). Three virion types (E1, E2 and E3) were cloned by repeated plaque purification of CB4-Edw and then all were compared relative to their effects on the pancreas of mice during acute infection. Seventy-two hours post-infection blood glucose, plasma amylase and insulin levels were monitored in mice of the SWR/J strain (previously classified susceptible to other diabetogenic picornaviruses), and the C57B1/6J strain (resistant). While all the viruses caused pancreatitis none of the animals infected with any of the clones showed as dramatic an increase in plasma amylase levels (four- vs 20-fold) as is characteristic of C57B1/6J mice inoculated with the original CB4 Edw virus. Greatest differences were expressed between the clones and CB4-Edw while less substantiative differences were found among the clones. For instance, clone E1 depressed blood glucose levels in C57B1/6J mice without affecting insulin levels. Likewise, the clone E2 depressed blood glucose levels without affecting insulin levels but only in SWR/J animals. This study demonstrates the heterogeneity of a human isolate of CB4. The subpopulation of virions contained within this isolate differ in the biological responses they elicit, specifically with regard to diabetogenic potential.

Amylases↗
PubMed1981

Biphasic development of the postnatal mouse pancreas.

Conventional biochemical and histological methods along with DNA flow-cytometric analysis were used (1) to define development of the mouse pancreas from birth to day 90 and (2) to provide information critical for studies on isolated islets and their component cells. Pancreas development in the mouse followed a biphasic pattern. Phase one extended from birth through day 15 and was dominated by proliferation and growth of endocrine cells as most islets attained adult form by day 15. Phase two, from day 15 through 30, was dominated by proliferation and growth of exocrine cells which became maximal by day 20. These data provide evidence suggesting that the optimum age for islet isolation is toward the end of phase one and before phase two, between days 10 and 15, and the optimum age for isolation of endocrine cells for proliferation and growth in culture is during the early part of phase one before most islets have attained adult form, between days 5 and 9.

Animals↗
PubMed1980

The role of host genetics in the pathogenesis of coxsackievirus infection in the pancreas of mice.

The susceptibility of mice to the diabetogenic effect of the M variant of encephalomyocarditis (MEMC) virus is probably inherited as a recissive trait. Three strains of mice that were susceptible to MEMC virus, three strains that were not susceptible to MEMC virus, and three types of F1 hybrid strains were infected with the common human coxsackie virus, group B, type 4 (CB4). They were examined to determine the titer of virus and histochemistry in the pancreas, levels of blood glucose, urinalysis, glucose tolerance, and levels of plasma amylase and insulin. There was a positive correlation between MEMC virus-susceptibility (diabetes-prone) and CB4-induced beta cell degranulation with concurrent hyperinsulemia and hypoglycemia. Also, as for MEMC virus, the titer of CB4 in the pancreas was not genotype-dependent. However, there was an inverse relation between destruction of the exocrine pancreas and the effect on the endocrine pancreas. These results suggest that the genetic factors responsible for the effect of MEMC virus on the endocrine pancreas are also responsive to CB4, and the proposed recessive nature of these factors is maintained for both viruses. In contrast, these factors, which are operatively recessive traits for the effect of CB4 on the endocrine pancreas, appear to be expressed as dominant traits with respect to the exocrine pancreas.

Animals↗
PubMed1980

The effect of smoke inhalation on pulmonary surfactant.

This paper details efforts to define the primary pathophysiology of acute smoke inhalation without the variables of infection, burns, or fluid resuscitation. A standard dose of smoke (wood and kerosene) was delivered at 37 C to mongrel dogs. The parameters studied included blood gases, carboxyhemoglobin, pulmonary and systemic hemodynamics, respiratory mechanics, surface tension area curves as an indication of surfactant activity, and in vivo photomicroscopy. The FiO2 of the smoke was 17 volumes per cent; the carbon monoxide 17,000 ppm. Immediately following smoke exposure, dense, nonsegmental atelectasis developed. Hemodynamic changes were insignificant, but the PaO2 fell to 49 mmHg; the right to left shunt rose from 5 to 41%. Surfactant reduction was significant: enough to cause an increase in the minimum surface tension from 7 to 22 dynes/cm. This surfactant loss may explain the atelectasis seen and the marked instability of subpleural alveolar walls. The data collected are consistent and support the acute inactivation of surfactant as one of the primary pathophysiologic events in smoke inhalation. The clinical correlation is good; surfactant loss may explain why victims of smoke inhalation are so vulnerable to fluid administration if they have thermal burns as well effectiveness of medical devices.

Animals↗