Biomedical subjects

D S Strayer

Publications and source records attributed to D S Strayer.

At least 73 records · Page 4Linked to original sources

PubMed1991

Immunogenicity of surfactant. I. Human alveolar surfactant.

The immunogenicity of lung surfactant derived from amniotic fluid has been well established. We have set out to examine the antigenic similarity of human surfactant to non-human alveolar surfactants currently being used therapeutically in clinical trials with neonatal respiratory distress syndrome. To this end, we raised a series of eight monoclonal antibodies in rats directed to human surfactant (H1 to H8). All antibodies bound human surfactant as measured by ELISA. Four of these monoclonal antibodies bound surfactant components by Western blot analysis: all bound a 9-10-kD species. In addition, one antibody (H2) bound a protein of 16 kD, one (H8) a 6-kD protein, and one (H6) a 30-kD protein. When mixed with surfactant, three antibodies, H4, H7 and H8, profoundly altered surfactant activity in vitro in the pulsating bubble surfactometer. Three other antibodies, H1, H2, and H5 moderately inhibited surfactant's surface activity. We also examined the cross-reactivity of these monoclonal antibodies with bovine (CLSE) and porcine (Curosurf) surfactants. By Western blot analysis, only H6 bound these heterologous surfactants. Other antibodies did so by ELISA. However, functional assays indicated that antibodies H7, H8 and H4 all greatly inhibited CLSE surface activity in vitro. Five antibodies (H1-H4 and H8) inhibited Curosurf function. Thus, human surfactant species, especially low molecular weight species, are highly antigenic. Antibodies to alveolar surfactants may inhibit surfactant function in vitro. As indicated by Western blot and cross-inhibition data, human lower molecular weight surfactants share epitopes with proteins from therapeutically important porcine and bovine surfactants. The potential importance of these findings to treatment of neonatal respiratory distress syndrome with heterologous surfactants is discussed.

Amniotic Fluid↗

PubMed1991

Immunogenicity of surfactant. II. Porcine and bovine surfactants.

Protein-containing surfactants of human and animal origin are being used increasingly to treat neonatal and adult respiratory distress syndromes. This trend led us to examine the antigenicity of two important preparations of animal surfactant, cow lung surfactant extract (CLSE) and a porcine surfactant preparation, Curosurf. We describe here 15 monoclonal antibodies against Curosurf and four against CLSE. Antibodies were studied by Western blot analysis to determine their ability to recognize protein components of their respective surfactant preparations. They were also tested for their ability to inactivate surfactant in vitro, assayed using the pulsating bubble surfactometer. Several antibodies directed against CLSE or Curosurf functionally inactivate the surfactant to which they were raised. We determined the degree of immunologic cross-reactivity between antibodies directed to CLSE and Curosurf against the other surfactant and also against human surfactant, both by Western blot and by examining functional inactivation in vitro. Antibodies to these animal surfactants that are commonly used therapeutically may inactivate the specific animal surfactant to which they were raised, as well as human and other surfactants. Generally, when antibodies inactivate surfactant from more than one animal species, they inactivate heterologous surfactants comparably to the extent to which they inactivate the surfactant to which they are directed. Immune complexes between anti-surfactant antibodies and surfactant have been described in the course of neonatal respiratory distress syndrome. The potential pathophysiological importance of anti-surfactant antibodies may therefore lie in their ability to inactivate administered surfactant, other similar surfactants and endogenous surfactant. In so doing, these antibodies may potentiate surfactant deficiency or pulmonary injury initiated by other stimuli.

Animals↗

PubMed1991

Effects of antisurfactant antibodies on the course of mild respiratory distress syndrome.

The role of surfactant-associated proteins in surfactant function was studied by selectively blocking these proteins with monoclonal antibodies. Four monoclonal antibodies, M1, M2, M3, and M4 were identified and their reactivities examined by Western blot analysis. M1, M2, and M4 bind, respectively, 8-, 10- and both 10- and 34-kD proteins. M3 antibody did not recognize a protein as assayed by this technique. These antibodies were then administered intratracheally to adult rats that had been partially depleted of lung surfactant by broncholavage. None of these antibodies had any deleterious effect on pulmonary function. On the other hand, M4 antibody significantly improved gas exchange. Possible mechanisms by which antibody may effect such improvement are discussed.

Animals↗

PubMed1991

In vivo and in vitro inactivation of bovine surfactant by an anti-surfactant monoclonal antibody.

In this study the importance of a low-weight surfactant protein (11 kDa) is demonstrated by selectively blocking this protein with a monoclonal antibody. In adult rats respiratory failure was induced by repeated bronchoalveolar lavage to remove all pulmonary surfactant. It was shown that surfactant mixed with the antibody was not capable of restoring lung function when compared with surfactant alone or surfactant mixed with control serum. Using the pulsating bubble surfactometer, it could be demonstrated that surfactant mixed with this antibody had a significant higher minimum surface tension when compared with surfactant alone, or surfactant mixed with an unrelated mouse immunoglobulin G (IgG). The inhibition of surfactant function by the monoclonal antibody suggests the importance of the 11 kDa protein for normal surfactant function.

Animals↗

PubMed1991

Identification of a cell membrane protein that binds alveolar surfactant.

Alveolar surfactants are complex mixtures of proteins and phospholipids produced by type II alveolar cells and responsible for lowering pulmonary surface tension. The process by which surfactant is produced and exported and by which its production by pulmonary cells is regulated are not well understood. This study was designed to identify a cellular receptor for surfactant constituents. To do so, monoclonal anti-idiotypic antibodies directed against antibodies to porcine and rabbit surfactant proteins were prepared. These monoclonal anti-idiotypic antibodies bind both alveolar lining and bronchial epithelial cells in rabbit, porcine, and human lungs. Macrophages and other nonepithelial cells do not react with these antibodies. Western blot analysis indicates that both A2R and A2C recognize the same proteins in both pig and rabbit lungs: a 30-kd protein and additional proteins at 52 and 60 kd. Preincubating lung wash cells with A2C or A2R prevents binding of porcine or rabbit surfactant preparations, respectively, by these cells. Preincubating frozen sections of lung tissue with surfactant inhibits binding of A2R and A2C to the lung. Antibody directed to a cell membrane protein that recognizes alveolar surfactant may be useful in elucidating the structure and function of this receptor and in understanding the cellular physiology and pathophysiology of the surfactant system.

Animals↗

PubMed1990

Molecular analysis of immunosuppression induced by virus replication in lymphocytes.

The relationship between immunosuppression and oncogenesis can be determined by studying the molecular interactions between tumor-inducing viruses and lymphocytes. We approached this study by using a unique system of two genetically related Leporipoxviruses, malignant fibroma virus (MV), and Shope fibroma virus (SFV). MV induces a syndrome of a highly lethal, disseminated myxosarcoma, severe immune suppression, and replicates in lymphocytes both in vivo and in vitro. In contrast, SFV causes a benign fibromyxosarcoma without immune dysfunction and cannot replicate in lymphocytes. Earlier studies demonstrated that transfer of a 10.8-kb Bam HI piece of MV (fragment "C") to SFV resulted in the ability of SFV to replicate in lymphocytes and suppress immune function. These results suggested that lymphocytotropic replication and immune suppression was located on the left side of fragment C. We extended these studies by generating families of recombinants between MV and SFV by using subfragments of fragment C. The resulting recombinant viruses were analyzed for their ability to replicate in lymphocytes, suppress immune function, and produce tumors. Those recombinants expressing MV-like characteristics were mapped by endonuclease digestion. This study demonstrates that recombinants containing a 3.6-kb Nde I subfragment, as well as those containing an overlapping 1.9-kb Hinc II subfragment, were capable of replicating in lymphocytes, suppressing immune functions, and inducing disseminated tumors in rabbits. Our study has therefore identified a portion of MV DNA sufficient to transfer the unique pathogenicity of MV to SFV, and suggests that control of immune suppression and tumor dissemination may not necessarily be mediated by the same viral genes.

Animals↗

PubMed1990

Natural cell-mediated immunity in the rabbit.

Susceptibility and resistance to tumors represent the interplay of many factors. One factor felt to govern the development of tumors is natural killer and natural cytotoxic cellular activity. The constitutional resistance of rabbits to spontaneous tumor development raises questions regarding the activity of natural cell-mediated immunity in this species. We therefore examined the ability of rabbit spleen, lymph node, and peripheral blood lymphocytes to mediate natural killer cell (NK) and natural cytotoxic cell (NC) activity in vitro. Using classical approaches to the study of NK and NC activity, we found no evidence of these activities in leporine spleen, lymph node, and peripheral blood lymphocytes. Preincubation of these cells with IL-2 did not induce such activity. Antibody-dependent cell-mediated cytotoxic reactivity (ADCC), which is believed to be mediated by NK cells, was also undetectable in rabbit lymphocytes. As controls, lymphocytes from other species were capable of mediating NK, NC, and ADCC functions normally in these experiments. Finally, we were unable to identify a population of large granular lymphocytes, the cells believed to mediate NK activity in other animals. Therefore, we could not demonstrate in the rabbit either natural cell-mediated immunity or the population of cells usually associated with natural cell-mediated immunity. If such activity exists in rabbits, it is different from that seen in other animals. More likely, the basis for the natural resistance of rabbits to tumor development must be sought elsewhere.

Animals↗

PubMed1990

Determinants of the ability of malignant fibroma virus to induce immune dysfunction and tumor dissemination in vivo.

The relationship of virus-induced immunological dysfunction and tumor dissemination was studied using two related tumor-causing leporipoxviruses: malignant fibroma virus (MV) and Shope fibroma virus (SFV). Recombinant viruses, produced by transferring MV's 10.7 kb BamHI C fragment to SFV, replicate in lymphocytes and suppress lymphocyte function in vitro. Those recombinants that replicate in lymphocytes and suppress lymphocyte function in vitro share about 3.5 kb from MV's C fragment. Some recombinants mimic MV in producing immune suppression and disseminated virus infection in vivo. Other recombinants, even some that are highly immunosuppressive in vitro (e.g. R71), only variably induce immune suppression in vivo, and do not cause disseminated disease. A segment of DNA from MV that transfers to Shope fibroma virus almost all of MV's virulence in vivo was identified.

Animals↗

PubMed1989

Arsenic-induced skin toxicity.

We reviewed available literature on the effects of inorganic arsenic on the skin to determine the potential hazards and to collate information regarding dosage and exposure to the incidence of skin cancer. Arsenic intake may result from occupational or medicinal exposure, or from drinking well water in areas with high arsenic levels in the soil. Arsenic causes a variety of benign skin lesions including hyperpigmentation and hyperkeratosis. Some hyperkeratotic lesions and squamous cell carcinomas in situ may progress to invasive carcinoma; other invasive squamous cell carcinomas will develop de novo. These cutaneous squamous cancers may metastasize; mortality is low, but has been reported. Locally invasive but non-metastasizing basal cell carcinomas may arise as well. These lesions occur in a characteristic pattern of distribution and are usually multiple. Observers reporting medicinally administered arsenic have described dose-response relationships between the amount of arsenic ingested and the frequency of various skin lesions. For arsenic found in drinking water, however, there is more controversy regarding the doses and exposure times necessary for cutaneous toxicity.

Arsenic↗

PubMed1989

Antigenicity of low molecular weight surfactant species.

The authors tested the antigenicity of human lung surfactant isolated from amniotic fluid. Mice and rabbits were immunized. Rabbit polyclonal antisera to these surfactant preparations were absorbed with normal human plasma proteins. Polyclonal antisera reacted with both high molecular weight (35 kd) surfactant apoprotein and to lower molecular weight species, both 18 kd and 9 kd. Mice were used to generate monoclonal antibodies to surfactant. Enzyme-linked immunosorbant assay was used to identify five monoclonal antibodies that reacted with surfactant. By Western blot analysis, all of these recognized a low molecular weight surfactant species (9 kd) that could be either SP-B or SP-C. One reacted with a 37 kd protein in the surfactant preparation, consistent with SP-A. One monoclonal antibody also recognized a higher molecular weight species (44 kd) of unknown origin. The ability of antisera and monoclonal antibodies to inhibit the functional activity of surfactant was assayed using a pulsating bubble surfactometer. Rabbit polyclonal antisera inhibited initial surface adsorption to equilibrium surface tension and increased the minimum surface tension after 1 and 5 minutes of initiation of pulsations. This inhibitory activity of the antisera was noted in divalent F(ab')2 fragments. Monovalent F(ab) fragments and control normal rabbit sera did not inhibit surfactant function in this assay. Of the anti-surfactant monoclonal antibodies that reacted with surfactant by ELISA and Western blot, three inhibited its capacity to lower surface tension on the pulsating bubble apparatus. The other two monoclonal antibodies showed no functional inhibitory activity. It is concluded that both the 35 kd SP-A and the 9 kd proteins of human surfactant are highly immunogenic and partially crossreactive. Resulting antibodies could alter the ability of surfactant to perform its physiologic function, ie, to lower surface tension.

Animals↗

PubMed1989

Surfactant replacement: immunological considerations.

We sought to analyse the potential immunogenicity of human alveolar surfactant as it is currently used in the treatment of neonatal respiratory distress syndrome (RDS). An enzyme linked immunosorbant assay capable of detecting specific immune complexes between surfactant and antibodies directed to surfactant was developed. Premature infants with RDS were divided into groups: one group received surfactant replacement and one received conventional therapy. Plasma samples obtained from these infants at birth and thereafter were examined for specific circulating immune complexes between surfactant and anti-surfactant antibodies. All babies were also examined for clinical and serological evidence of immune complex-mediated tissue damage. We found that almost all infants with RDS, regardless of their therapy, showed evidence of circulating surfactant-anti-surfactant immune complexes. Plasma samples from infants without RDS showed no such complexes. Immune complexes appeared early in postnatal life, usually within the first week, and diminished thereafter. We detected no evidence of altered plasma complement levels or end organ damage attributable to these immune complexes. Thus, circulating immune complexes between surfactant and antibodies to surfactant are common in neonatal respiratory distress syndrome, though they do not appear to cause injury. Since not only human but heterologous surfactants are now used in treating RDS, we feel that cautious evaluation of potential immune reactions to the administered materials should be undertaken.

Antigen-Antibody Complex↗

PubMed1988

Immunosuppression during viral oncogenesis. V. Resistance to virus-induced immunosuppressive factor.

Rabbits given malignant rabbit fibroma virus (MV) develop severe immunologic dysfunction during the course of infection. Splenic T lymphocytes from these rabbits elaborate a soluble non-specific immunosuppressive factor (virus-induced suppressor factor (VISF]. As malignant rabbit fibroma virus infection progresses, normal immunologic responsiveness returns. This recovery is multi-factorial and involves production by T lymphocytes of a soluble factor capable of antagonizing the activity of VISF. This soluble anti-suppressor factor (ASF) is not a generalized immunologic potentiator. Its sole apparent effect on immune function appears to be to antagonize the activity of VISF. The protective effects of ASF are evident only when suppressor factors and ASF are simultaneously present in culture. Pre-treatment of target cells with ASF-containing culture supernatants does not render them insensitive to the immunosuppressive effects of subsequent treatment with VISF. In addition, ASF appears to be directly responsible for antagonizing VISF activity. That is, ASF does not appear to initiate an anti-suppressive cascade by activating a population of cells that in turn generate secondary protective factors. ASF-producing cells do not bind Vicia villosa lectin, as do contra-suppressor cells described by others. In almost all of these features, the system we describe herein differs from systems in which other investigators have described factors that antagonize the effects of suppressor factors.

Animals↗

PubMed1988

Immunosuppression during viral oncogenesis. IV. Generation of soluble virus-induced immunologic suppressor molecules.

We describe herein functional attributes and generation of immunologic suppressor activity elaborated in response to oncogenic virus infection. Malignant rabbit fibroma virus-induced immunologic suppressor factor (VISF) is a T cell product produced in peak quantities by spleen cells taken from infected rabbits 7 days after infection in vivo. Its production does not appear to require macrophage participation. VISF is highly labile, 3.5 to 12 kDa, and capable of suppressing both B and T lymphocytic responses. Indomethacin and the cyclic nucleotides cAMP and cGMP inhibit its generation. VISF activity is neither antigen nor species specific. It suppresses murine and leporine immune responses to antigens unrelated to the inducing virus. Comparable suppressor activity may be induced by infecting an apparently non-functional rabbit T lymphoma line, RL-5, with malignant rabbit fibroma virus. VISF is principally a suppressor-inducer factor: in vitro, lymphocytes exposed to VISF do not show decreased immunologic responsiveness until 4 days of culture. VISF induces T suppressor cell activity when normal spleen cells are exposed briefly to VISF. Thus, immunosuppressive consequences of malignant fibroma virus infection are partially mediated by a small, non-specific T cell-derived suppressor lymphokine with unique functional characteristics. Non-specific immunologic dysfunction that often attends virus infections may reflect the activity of such factors in humans as well.

Animals↗

PubMed1988

Lymphocyte-virus interactions. Identification of a restriction fragment permitting virus replication in lymphocytes.

We are interested in understanding the effects of virus infection on lymphocyte function. To approach this question, we used a unique system of two genetically related leporipoxviruses to generate recombinants. One of these viruses, malignant fibroma virus (MV), replicates in many different cell types, including lymphocytes. The other, Shope fibroma virus (SFV), replicates principally in fibroblasts, but cannot replicate in lymphocytes. Fibroblasts infected with SFV received restriction fragments from MV by transfection. Recombinant viruses were selected in vitro for their ability to replicate in lymphocytes. By these means we have identified one restriction fragment, the 10.8-kb BamHI "C" fragment, capable of transferring from MV to SFV the ability to replicate in lymphocytes. A family of recombinants bearing different sized inserts of this restriction fragment has been isolated and is being characterized. Lymphocytotropic recombinants bearing portions of this restriction fragment produce colony morphology in vitro intermediate between MV's plaques and SFV's foci. On the basis of their ability to grow in and suppress mitogen responsiveness of lymphocytes, these recombinants may be classified into four different groups. Group 1 viruses are the most immunosuppressive, whereas those of group 4 are least. These traits correlate with ability to replicate in lymphocytes. Genetic analysis of recombinants indicates that the most immunosuppressive recombinants do not necessarily contain the most fragment C DNA. Therefore, we have identified a restriction fragment, one or more of the genes of which are sufficient to allow an otherwise nonlymphocytotropic virus to replicate in lymphocytes. Additional genetic and immunologic analysis should permit us to determine the structure and function of the protein responsible for this effect.

Animals↗

PubMed1988

Immunologic consequences of exogenous surfactant administration.

In conclusion, we have shown that human surfactant is immunogenic and that circulating surfactant-antisurfactant immune complexes are detectable in the plasma from infants and in adults with RDS. We found these immune complexes regardless of whether exogenous surfactant was used in the individual treatment regimen. These immune complexes do not yet seem to cause disease in the short term. Long-term effects, if any, are unknown. Indications for surfactant replacement therapy in neonatal RDS are clear. Trials of exogenous surfactant are just beginning in adult RDS, and potential immunogenicity will be of even greater concern in these patients. In all such situations, potential for side effects must be balanced against therapeutic efficacy and the gravity of the disease. Our data indicate that surfactants, particularly heterologous surfactants, are potent immunogens. One cannot assume that using homologous or heterologous surfactants in patients with RDS will always be immunologically innocuous. Nonetheless, based on present data, moderately long-term follow-up (2 to 4 years), we are encouraged by our observation that no selective adverse effects attributable to human surfactant have been recognized, yet mortality from RDS in infants less than 30 weeks has been nearly cut in half.

Adult↗

PubMed1987

Growth of malignant rabbit fibroma virus in lymphoid cells.

To understand better the immunosuppressive capacity of malignant rabbit fibroma virus (MV), we characterized MV growth in lymphoid cells. Replication of MV occurs in unstimulated normal spleen cells in vitro and is enhanced by adding T- or B-lymphocyte mitogens. In splenic T-lymphocyte preparations, comparable results are found: virus growth in the absence of mitogen, augmented by adding Con A. Unlike mature T cells, thymic lymphocytes support MV replication only when mitogen is added. When spleen cells from rabbits infected with MV in vivo are removed and cultured without mitogen, MV growth is again observed, with virus titer increasing about 10-fold per day of culture. In spleen cell populations from MV tumor-bearing rabbits, MV grows best in T lymphocytes, moderately in B lymphocytes, and least efficiently in adherent cells. When spleen cells are examined immediately following sacrifice, MV antigens are expressed solely on T lymphocytes from rabbits infected in vivo with MV 7 days previously. However, following overnight incubation in vitro a population of non-T lymphocytes displays cell membrane virus antigens. MV adapts itself somewhat to growth in lymphocytes, showing significantly greater growth in lymphocytes following passage in lymphocytes than is observed for non-lymphocyte-propagated virus. MV-infected lymphocytes also elaborate a factor that enhances MV growth in lymphocytes. Thus, MV replicates preferentially in mature T lymphocytes but will grow well in B cells as well. In vivo infection produces relatively small amounts of recoverable virus. However, when these lymphocytes are cultured in vitro virus replicates very well without added mitogens. These growth patterns may help to understand MV-induced immunologic dysfunction.

Animals↗

PubMed1987

Virus-lymphocyte interactions during the course of immunosuppressive virus infection.

Malignant rabbit fibroma virus (MV) is a lymphocytotropic leporipoxvirus which produces profound immunological dysfunction and lethal fibromyxosarcoma. We examined virus recovery from splenic lymphocytes as a function of time after inoculation in vivo, and correlated this with both immunological function and expression of virus-induced host suppressor activity. MV was most abundant in lymphocytes obtained 4 days following inoculation. At that time, immune function was relatively normal and host suppressor activity was not observed. By 7 days after infection, when active host immunosuppressor functions were observed, virus recovery was decreased. Eleven days post-inoculation host immune function began to recover despite increasing virus-induced tumours and developing opportunistic infection. Simultaneously, MV was no longer recoverable from spleen cells. Spleen cells from day 11 tumour-bearing rabbits did not support MV replication as efficiently as did normal or day 4 or 7 splenic lymphocytes, but they did not alter the ability of MV to grow in the latter cells. By fluorescence examination and cytofluorography, splenic lymphocytes bearing MV antigens were abundant 7 days after infection but disappeared by 11 days. This was temporally related to production of neutralizing antibody to MV, and development of virus-specific lymphocyte proliferative activity. The composition of splenic lymphocytes changed as well: the normal ratio of about 1:1 for B and T cells changed to 1:2 by day 7, and then inverted to almost 2:1 by day 11. Rabbits infected with MV thus appear to recover their immune function, concurrently eliminate virus-infected lymphocytes, and elaborate high titres of neutralizing serum antibodies despite progressive infections and tumour development.

Antibodies, Viral↗

PubMed1987

Inhibition of epidermal growth factor-induced cellular proliferation.

The authors tested whether two oncogenic poxviruses, Shope fibroma virus (SFV) and malignant rabbit fibroma virus (MV), coded for an epidermal growth factor (EGF)-like protein. Virus-free lysates of SFV or MV-infected rabbit kidney cells do not appreciably affect proliferation of EGF-unresponsive RK-13 cells. Comparable lysates inhibit the background proliferation of two EGF-responsive cell lines, human foreskin fibroblasts and normal rat kidney cells. Inhibition of EGF-stimulated proliferation is also observed in a dose-dependent fashion. This inhibition is greatest when the virus lysate preparations are added either simultaneously with or before EGF. When EGF is added to cultures 24 hours before the SFV or MV preparations, the latter then have little or no effect on EGF-induced target cell proliferation. The inhibitory factor competed with radiolabeled EGF for its receptor site. Electroblotting shows a protein of 35 kd molecular weight in the lysates of virus-infected RK-13 cells which reacts with anti-EGF antibody. These findings interpreted to indicate that SFV and MV code for an inhibitor of EGF activity, and that this inhibition occurs at least in part by competitive inhibition of EGF-EGF receptor interactions.

Cell Division↗