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D A Weigent

Publications and source records attributed to D A Weigent.

At least 37 records · Page 2Linked to original sources
PubMed1991

Detection of growth hormone and growth hormone-releasing hormone-related messenger RNA in rat leukocytes by the polymerase chain reaction.

To validate that growth hormone (GH) and growth hormone-releasing hormone (GHRH) can be produced by leukocytes, we have assessed the presence of GH and GHRH-related mRNA in leukocyte cultures by reverse transcription and the polymerase chain reaction. A sample of the polymerase chain reactions were size-fractionated by electrophoresis in a 0.8% agarose gel and examined with ultraviolet light after ethidium bromide staining. Single major DNA bands corresponding in length to the distance between the 5' ends of the two GH and GHRH specific primers, 603 base pairs and 260 base pairs, respectively, were obtained. The DNA bands hybridized specifically to GH- and GHRH-specific probes after Southern transfer to nitrocellulose. The identity of the GH polymerase chain reaction material was confirmed by restriction enzyme analysis. The results showed that GH and GHRH gene expression occurs in mononuclear leukocytes and support the idea that these neuroendocrine hormones may be common signal molecules between the immune and neuroendocrine systems.

Animals↗
PubMed1990

Bidirectional communication between the neuroendocrine and immune systems. Common hormones and hormone receptors.

The results reviewed here support a molecular basis for bidirectional communication between the immune and neuroendocrine systems. The main findings can be summarized as follows: First, cells of the immune system can synthesize biologically active neuroendocrine peptide hormones. Second immune cells also possess receptors for many of these peptides. Third, these same neuroendocrine hormones can influence immune function; and fourth, lymphokines can influence neuroendocrine tissues. The interesting conceptual advance is the idea that the immune system may serve as a sensory organ. Thus, the immune system may sense stimuli that are not recognized by the central or peripheral nervous system. These stimuli are termed noncognitive and include bacteria, viruses, tumors and antigens. The recognition of such stimuli is converted into information in the form of lymphokines, monokines, and hormones and a message received by neuroendocrine tissues. On the other hand, nervous system recognition of stimuli can also be converted into chemical signals that can be relayed to immune cells resulting in physiological changes. On this basis, we predict that the pathophysiology associated with infectious agents may be related to the types and amounts of hormones produced by the immune system.

Animals↗
PubMed1989

Expression of growth hormone by lymphocytes.

In the present study, we evaluated whether mononuclear leukocytes could synthesize and secrete growth hormone (GH) in vitro. Studies using antibody affinity chromatography, high pressure liquid chromatography, and polyacrylamide gel electrophoresis indicate that leukocytes secrete a approximately 22,000 dalton molecular weight immunoreactive GH (irGH). The irGH appeared to be de novo synthesized since it could be radiolabeled with tritiated amino acids and its production blocked by prior incubation of leukocytes with cycloheximide. The levels of secreted irGH were enhanced by concanavalin A or lipopolysaccharide. By using RNA slot blot analysis, we detected specific GH mRNA present in the cytoplasm of rat leukocytes. Leukocytes from a variety of tissues in rats, including spleen, thymus, bone marrow, and peripheral blood as well as separated spleen T and B cells, were all observed to produce GH RNA and secrete GH from the cells. We conclude that lymphocytes produce a mRNA for irGH and are then able to translate that message and secrete the molecule from the cell. The data suggest a potential regulatory loop between the immune and neuroendocrine systems.

Animals↗
PubMed1989

Hormones common to the neuroendocrine and immune systems.

Considerable progress is now being made in studies of the interactions between the immune and neuroendocrine systems, and the relevance of the results to many disease processes is increasingly recognised. Recent published, and hitherto unpublished, work on one aspect of this topic--the production and function of neuroendocrine hormone by cells of the immune system--is herein summarised by a foremost investigator and his colleagues. Evidence is presented that several peptide hormones (ACTH, endorphins, thyrotropin, chorionic gonadotropin, growth hormone) are produced constitutionally, or in response to stimulation, by cells of the immune system, and there is speculation as to their roles in local immune response, endotoxic shock, antibody production, pregnancy, and in the diagnosis of specific psychiatric and neuroendocrine disorders. The review and commentary contribute to fuller understanding of the underlying molecular biology, from which new opportunities in rational drug design will undoubtedly emerge.

Animals↗
PubMed1988

Production of immunoreactive growth hormone by mononuclear leukocytes.

In the present study, we evaluated whether mononuclear leukocytes could synthesize and secrete growth hormone (GH) in vitro. By using RNA slot blot analysis, we detected maximum spontaneous levels of specific GH mRNA in the cytoplasm of rat leukocytes after a 4-h incubation. Northern gel analysis demonstrated that the specific leukocyte GH RNA was polyadenylated and had a molecular mass of 1.0 kb. Further studies using immunofluorescence, antibody affinity chromatography, and Sephacryl gel filtration indicate that leukocytes secrete a high molecular weight (greater than 300,000) and a low molecular weight (approximately 22,000) immunoreactive GH (irGH). A substantial amount of the high molecular weight irGH can be converted to the lower molecular weight form after reduction with mercaptoethanol. The irGH appeared to be de novo synthesized because it could be radiolabeled with tritiated amino acids and its production could be blocked by previous incubation of leukocytes with cycloheximide. The replication of Nb2 rat node lymphoma cells was stimulated by affinity-purified human lymphocyte-derived irGH. The growth stimulation was blocked by specific antibodies to hGH. We conclude that lymphocytes produce an irGH that is similar to if not identical to pituitary GH in terms of bioactivity, antigenicity, and molecular weight. The findings demonstrate a potential regulatory loop between the immune and neuroendocrine tissues.

Animals↗
PubMed1988

Individuals infected with HIV possess antibodies against IL-2.

Studies are presented here which demonstrate that antibodies reacting with human interleukin-2 (IL-2) are present in the sera of patients infected with the human immunodeficiency virus (HIV). It is likely that these antibodies are present due to a homology between the HIV envelope protein and IL-2. The homologues are six amino acids in length corresponding to the carboxy terminus of gp41, Leu-Glu-Arg-Ile-Leu-Leu (LERILL), and residues 14-19 of secreted IL-2, Leu-Glu-His-Leu-Leu-Leu (LEHLLL). Thus, we questioned whether antibodies made against this HIV envelope peptide would cross-react with IL-2. Not only do a high percentage of the HIV-infected individuals tested here have antibodies against LERILL, but these antibodies cross-react with the IL-2 sequence, LEHLLL. Additional antigenic processing of IL-2 is suggested by the finding that epitopes other than this sixmer are also recognized by antibodies in patients' sera. Thus, these studies suggest a mechanism by which infection with HIV can induce a potentially suppressive autoimmune response. Specifically, antibodies against an HIV envelope peptide cross-react with an epitope in IL-2.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Antibodies to the carboxyl terminus of mouse interferon-gamma neutralize its immunoregulatory and antiviral activities.

Antibodies to a synthetic carboxy-terminal peptide (Cys-Ser-Leu-Arg-Lys-Arg-Lys-Arg-Ser-Arg-Abu) (gamma-C-TP) of mouse interferon-gamma (MuIFN-gamma) were produced in rabbits. They neutralized the antiviral activity of MuIFN-gamma but not that of MuIFN-alpha/beta or human (Hu) IFN-alpha/beta or -gamma. They also inhibited the IFN-dependent enhancement of natural cytotoxic cells (NCC) and the in vivo plaque-forming cell (PFC) response to sheep red blood cells (SRBC). Thus, our results indicate that polyclonal antibodies specific for the nine carboxy-terminal amino acids of MuIFN-gamma can specifically inhibit the antiviral and immunoregulatory activities of this IFN in vitro. In addition, our findings indicate that endogenous production of MuIFN-gamma in vivo plays a role in development of the full antibody response to SRBC surface antigens.

Animals↗
PubMed1987

Interferon review.

Although IFN proteins were recognized first for their potent antiviral properties, it has now been established that they may profoundly affect other vital cellular functions. The IFNs are divided into three main classes, alpha, beta, and gamma, and are defined by their differences in amino acid sequences, physicochemical properties, and induction by different agents from different cell types. The inducing agents include viruses, bacteria, bacterial products, polymers, low molecular weight compounds, and antigens or mitogens. Studies on the mechanisms of action of IFNs have mainly been focused on their antiviral actions. However, many of the facts revealed by these studies are equally relevant for understanding other actions of IFN. IFNs are extremely potent, they interact with specific receptors, and they induce the expression of specific genes, the products of which mediate their various actions. There is almost a complete lack of knowledge of what happens between the interaction of IFN with its receptor and induction of new RNA synthesis. However, we are beginning to understand how some of the IFN-inducible enzymes impair viral replication. The discovery of the dsRNA-dependent enzymes has implications beyond the IFN system. It is quite possible that they are used for other physiologic regulatory systems as well. The identities and functions of many other IFN-inducible proteins remain to be elucidated. Principally, IFNs alpha and beta are cytokines in that they may be produced by the cellular components of the immune system and have immunoregulatory effects on the cells of the immune system. These effects include enhancement of surface structures such as histocompatibility antigens, pleiotropic hormone-like effects, and stimulation or inhibition of the activities of a number of different effector cells such as B cells, T cells, macrophages, and natural killing cells. IFN levels may be below detection and yet mediate important biologic functions. Perhaps the most interesting IFN subtype regarding immunoregulation is IFN gamma, which is a product of T lymphocytes. Few drugs have stimulated as much research interest or clinical promise as the IFNs. Clinical trials in patients have shown most promise in coryza, herpes virus infections, papilloma virus tumors, hairy cell leukemia, multiple myeloma, and renal cell carcinoma. IFN gamma employed alone and in combination with IFN alpha may dramatically increase IFN's activity. IFN treatment combined with chemotherapy also may give enhanced antitumor activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Interactions between the neuroendocrine and immune systems: common hormones and receptors.

The studies reviewed here support a molecular basis for bidirectional communication between the immune and neuroendocrine systems. The main findings can be summarized as follows: First, cells of the immune system can synthesize biologically active neuroendocrine peptide hormones. Second, immune cells also possess receptors for many of these peptides. Third, these same neuroendocrine hormones can influence immune function; and fourth, lymphokines can influence neuroendocrine tissues. Although recent studies have begun to unravel the biochemistry of bidirectional communication between the immune and neuroendocrine systems, there are still missing parts in this puzzle. Among the important questions that must be resolved are the identification of factors that trigger the synthesis of neuroendocrine hormones by immune cells. Are these events operating similar to or in balance with pituitary cells? Drugs that interfere with either pathway may be useful. Second, it will be of value to understand the factors controlling neuroendocrine hormone receptor expression on immune cells. A better understanding of the spectrum of positive and negative regulatory events for both systems may determine the ultimate behavior of immune and neuroendocrine cells. In addition, since leukocytes can produce hormones and also have receptors for the same hormones (e.g., ACTH and GH), it is possible that these immunocytes may also influence their own function in an autocrine-like fashion. We have postulated that the immune system can serve as a sensory organ for external stimuli that cannot be detected by the nervous system (Blalock 1984). Thus, the immune system recognizes stimuli such as bacteria, viruses or tumors, whereas the nervous system detects classical sensory stimuli. The contribution of extrapituitary sites of hormone production and function may provide new clues to define psychological and/or pathological states in the pathophysiology of infectious diseases and tumors.

Animals↗
PubMed1986

The HTLV-III envelope protein contains a hexapeptide homologous to a region of interleukin-2 that binds to the interleukin-2 receptor.

A region of human interleukin-2 (IL-2) which was predicted to be a contact point with its receptor was used to locate a homologous region in the envelope protein of human T-lymphotropic retrovirus (HTLV-III). This homologous six amino acid peptide from the carboxy (C)-terminus of the HTLV-III envelope protein was found to inhibit the biological activity of human IL-2 in a murine spleen cell proliferation assay. When conjugated to a carrier protein, this peptide inhibited the binding of radiolabelled IL-2 to its receptor. The biological activity of the peptide was antagonized by a six amino acid peptide fragment of the IL-2 receptor which was predicted to be the contact point on the receptor that corresponded to the binding region of IL-2. The HTLV-III peptide also inhibited the binding of radiolabelled IL-2 to polyclonal anti-IL-2 antiserum. These data support the previous assignment of contact points between IL-2 and its receptor. They also suggest two possible mechanisms of immunosuppression during acquired immunodeficiency syndrome (AIDS). One involves direct competition of the envelope protein or its fragments with IL-2 for binding to the IL-2 receptor. The other involves antibodies to the envelope protein which crossreact with and neutralize IL-2.

Amino Acid Sequence↗
PubMed1986

Pretreatment of human lymphocytes with interferon enhances the synthesis of interferon in cocultures with allogeneic cells.

Human lymphocytes pretreated with interferon (IFN) alpha, beta, or gamma produced 17 times more IFN alpha (600-10,000 units/ml) than nontreated lymphocytes when cocultivated with allogeneic cells. Significant increases in IFN production (500-3,000 units/ml) were observed when lymphocytes were treated with IFN for just 2 h, and peak levels (10,000 units/ml) were produced after a 4-h treatment. The amount of IFN required to show the maximum priming effect was between 100 and 1,000 units; higher levels of IFN were inhibitory. The levels of IFN increased as the lymphocyte-to-target-cell ratio increased from 2:1 to 10:1 and decreased at higher ratios. The decrease in IFN production at higher ratios of lymphocytes to target cells could not be attributed to the presence of a soluble suppressor substance. The additional IFN found in supernates was attributed to enhanced production of IFN by the same cells, rather than recruitment of more cells to produce IFN. This conclusion is based on the fact that no increase in the number of cells staining positive for IFN production was observed in primed lymphocytes. The increased amount of IFN due to priming enhanced both nonsensitized cytotoxic activity and the transfer of antiviral activity, which could be prevented by antibody to IFN. The data suggest that priming may be an important biological mechanism for obtaining significant levels of IFN more rapidly in the vicinity of transformed cells or virus-infected tissues.

Cells, Cultured↗
PubMed1986

Role of interferon in streptococcal infection in the mouse.

In previous studies, we have shown the rapid in vitro induction of IFN gamma from human T cells by highly purified peptic extracts of M proteins from Streptococcus pyogenes. The present report extends these in vitro studies and shows that a mixture of both alpha/beta and gamma IFN were present in spleen cell homogenates after in vivo treatment with M protein wild-type (M+) or mutant (M-) S. pyogenes strains. The levels of bacterial-induced IFN were found to be greater in M+ treated animals. Additional studies in vivo showed that pretreatment of mice with heat-killed M+ S. pyogenes organisms significantly protected mice to pneumococcal infection compared to similarly treated M- or control animals (P less than 0.001). Further, antibodies to mouse IFN alpha/beta and antibodies specific to a synthetic N-terminal peptide of mouse IFN gamma enhanced the death of animals due to pneumococcal infection and blocked the protection observed in animals previously treated with heat-killed M+ organisms. Most importantly, treatment of mice with either type of IFN alone enhanced the survival of mice to levels similar to that observed by treatment with M+ organisms (P less than 0.05). The results strongly suggest that IFN can play a crucial role, directly or indirectly, in controlling infection by Streptococcus pneumoniae and perhaps other streptococci.

Animals↗
PubMed1985

Streptococcus pneumoniae cocultured with fibroblasts enhances both interferon production and cytotoxic activity by lymphocytes.

Cell-mediated cytotoxicity against normal human fibroblasts was dependent on treatment of the fibroblasts with Streptococcus pneumoniae. Both spontaneous and interferon (IFN)-enhanced lymphocytes killed human foreskin (HFS) or skin muscle cells cocultured with S. pneumoniae five- to eightfold more than control nontreated cells. Based on Percoll gradient centrifugation, the cytotoxic effector cell migrated like a large granular lymphocyte. The human IFN produced from mixtures of HFS cells, lymphocytes, and S. pneumoniae was observed to be both a mixture of IFN-alpha and IFN-gamma and in an amount 500 times greater than that observed with lymphocytes on HFS cells alone, and it was in an amount 12 times greater than when lymphocytes and bacteria were cultured together. A mixture of antibodies to IFN-alpha and -gamma added to cocultures of fibroblasts and bacteria blocked the killing of fibroblast targets by lymphocytes (47 versus 13%). Thus, endogenously produced IFN was essential for the effective killing of the fibroblasts. Treatment of HFS cells with IFN before bacterial treatment protected the HFS cells from lysis by lymphocytes. The observation that normal diploid cells exposed to bacteria can be killed by lymphocytes suggests that natural cytotoxic cells are active at the site of bacterial infection and conceivably play roles in defense or pathogenesis.

Bacterial Infections↗
PubMed1985

Interferon-induced transfer of natural cytotoxic activity between human leukocytes.

Interferon (IFN) caused the transfer of natural cytotoxic activity between human leukocytes in a syngeneic system. The transfer of cytotoxic activity was found to be dependent on the cell density and was in proportion to the IFN concentration. Human immune-type IFN (IFN-gamma) was more efficient than IFN-alpha or IFN-beta in eliciting the transfer of cytotoxic activity. The transfer occurred with IFN-gamma preparations of various specific activities and with recombinant IFN-gamma. The transferred activity had the characteristics of an IFN-induced antiviral state, in that it was blocked either by actinomycin D or by prevention of cell contact. Specific antibodies to IFN had no effect on the transfer of cytotoxic activity. Protection of mouse target cells from human cytotoxic activity could also be transferred from IFN-induced human foreskin fibroblasts (HFF) insensitive to cytotoxic activity to the cytotoxic-sensitive mouse cells. The transfer of protection was highly efficient at ratios of one HFF cell to 16 mouse target cells. The transfer of cytotoxic activity, and protection from cytotoxic activity, may represent a mechanism for amplification of the IFN system as a host defense against viral-infected or tumor cells.

Animals↗
PubMed1984

Interferon-induced transfer of viral resistance by human B and T lymphocytes.

Enriched human B lymphocytes cocultivated with mouse L cells produced human leukocyte interferon (IFN-alpha) and shortly thereafter transferred antiviral activity to the recipient cells (99% inhibition of expected virus yield). In contrast, cocultivation of enriched T-cell populations with mouse L cells resulted in no IFN production or transfer of antiviral activity. In addition, both T and B lymphocytes pretreated with exogenous IFN or stimulated in vitro by mitogens could transfer antiviral activity to human WISH cells. The transfer of antiviral activity was not blocked by antibodies to IFN. The data indicate that both T and B cells can be recruited by IFN to transfer antiviral activity. Thus, once cells are recruited by IFN they can transfer antiviral activity in the absence of IFN and protect cells locally or distally from the site of infection.

Animals↗
PubMed1984

Induction of human gamma interferon by structurally defined polypeptide fragments of group A streptococcal M protein.

The presence of interferon (IFN) has been demonstrated previously (i) in fluids obtained from the middle ears of children with Streptococcus pneumoniae infections, (ii) from the serum of mice injected intraperitoneally with either S. pneumoniae or Streptococcus pyogenes, and (iii) from human lymphoid cell cultures treated with a variety of bacteria. In this study, we showed that highly purified peptic extracts of three different serotypes of group A streptococcal M protein (pep M5, pep M6, and pep M24) stimulated human peripheral leukocytes to produce IFN. IFN production was apparent by 10 h and peaked 24 h after exposure. Dose-response experiments indicated that IFN could be detected in cultures treated with concentrations of M protein as low as 6 micrograms/ml, whereas maximum IFN production occurred at a concentration of 200 micrograms/ml. The IFN had antigenic and physicochemical characteristics of IFN-gamma. Preliminary leukocyte fractionation studies revealed that the IFN-producing cell was a nonadherent lymphocyte with receptors for sheep erythrocytes (T cell). Rabbit antisera specific for these structurally defined polypeptide fragments of streptococcal M protein (pep M5, pep M6, and pep M24) blocked IFN induction by each of the polypeptides. The data suggest that the different serotypes of streptococcal M protein may induce IFN by a common structural determinant shared by each of the polypeptide fragments tested.

Amnion↗
PubMed1984

Synergism of antiviral activity in cell cultures treated with low concentrations of interferon and interferon-treated lymphocytes.

Human T cells treated with low levels of interferon (IFN) (1-10 units/ml), and washed to remove the IFN, transferred the same level of antiviral activity to recipient WISH cells as an equivalent IFN treatment alone could induce in WISH cells. Further, when T cells pretreated with IFN (1-10 units/ml) were cocultivated with WISH cells in the presence of IFN (1-10 units/ml), a 2.5- to 5-fold greater level of protection developed than could be expected from the additive effect of each. Antibody to leukocyte, fibroblast, or immune IFN blocked the antiviral effect of the respective IFN types but had no effect on the transfer of antiviral activity initiated by leukocyte, fibroblast, or immune IFN. Also, treatment of T cells with actinomycin D blocked the transfer of antiviral activity of IFN-treated T cells. Taken together, the data suggest that the increased antiviral activity is not merely an additive effect of the IFN, but represents a synergistic amplification of protection most likely due to the combination of the separate effects of IFN and IFN-induced transfer. Such interactions would be expected to play a major role in early protection against virus infections in vivo when low levels of interferon are present and lymphocytes are migrating into the area.

Amnion↗