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Biomedical subjects

E L Morgan

Publications and source records attributed to E L Morgan.

At least 19 recordsLinked to original sources
PubMed1992

Identification and characterization of the effector region within human C5a responsible for stimulation of IL-6 synthesis.

Human C fragment C5a is known to be a proinflammatory mediator and more recently shown to be a potent modulator of both humoral and cell-mediated immunity. We recently reported that natural and recombinant C5a induces the synthesis of IL-6-specific mRNA and secreted protein from human monocytes. Our studies using analogue peptides that are homologous to the carboxyl-terminal sequence of human C5a, indicate that the "effector" site for inducing IL-6 synthesis resides within the C-terminal region (C5a (70-74)) of the C5a molecule. C5a peptides containing the exact sequence of the natural factor were found to retain full agonist activity but exhibited low potency (0.01-0.1% of intact C5a). It was also shown that amino acid substitutions in the C5a peptides by aromatic/hydrophobic residues, outside the immediate effector site, resulted in analogue peptides with a substantial increase in potency relative to the most active natural peptide (C5a (56-74)). Moreover, these peptides approach the potency of natural C5a for induction of IL-6. Taken together, these results suggest that the inflammatory and immunoregulatory activities associated with C5a may, in part, be due to the synthesis of IL-6.

Amino Acid Sequence↗
PubMed1991

Fibronectin augments anti-CD3-mediated IL-2 receptor (CD25) expression on human peripheral blood lymphocytes.

The extracellular matrix (ECM) is composed of a number of macromolecules that promote cell adhesion, cell migration, and differentiation. Receptors for these molecules have been identified and belong to a superfamily of cell surface proteins, collectively known as the integrins. In this study, we show that the matrix protein fibronectin (FN) acts synergistically with immobilized anti-CD3 antibody to promote proliferation of total human peripheral blood lymphocytes (HPBL) in the absence of exogenous IL-2. Proliferation was inhibited by both the alpha 5 beta 1 and alpha 4 beta 1 recognition peptides. ARG-GLY-ASP (RGD), and GLU-ILE-LEU-ASP-VAL-PRO-SER-THR (EILDVPST), respectively. Expression of CD25 (IL-2 receptor) was significantly higher on cells cultured on anti-CD3 and FN, indicative of T-cell activation. Additionally, cells cultured on immobilized anti-CD3 and FN for 3 days showed increased adhesion to FN and increased forward light scatter/side scatter profile. Synthesis of both IL-1 and to a lesser extent IL-2 was elevated in supernatants from cultures containing both anti-CD3 and FN. These data are consistent with published reports which demonstrate that ECM proteins can act as costimulants of lymphocyte proliferation. Finally, our results show that cells cultured on anti-CD3 antibody and FN have an activated phenotype and that cytokines may be involved in this process.

Antibodies↗
PubMed1990

Induction of human B cell differentiation by Fc region activators. II. Stimulation of IL-6 production.

Fc region fragments derived from the enzymatic cleavage of human IgG have been shown to induce human peripheral blood-derived B cells to differentiate into Ig secreting cells (ISC). The synthetic peptide p23, corresponding to residues 335 to 357 in the Fc region of human IgG1, represents a region of the molecule responsible for stimulation of ISC formation. Fc region-induced ISC formation requires at least two signals; one supplied by Fc region activators and one supplied by a T cell-derived factor(s). In this report we show that the coculture of human PBMC with pFc' or p23, results in the release of factor(s) that resemble IL-6 in its pattern of biologic activity. This conclusion is based on the observations that supernatants from Fc region-stimulated PBMC cultures contained increased levels of elements that scored as positive in two assays for IL-6: the B9.9 hybridoma growth and the CESS cell differentiation assays. Moreover, RNA from Fc region-stimulation PBMC contained increased levels of IL-6 cDNA-hybridizable elements. Finally, it was observed that rabbit anti-IL-6 inhibited the ability of supernatants derived from Fc region-stimulated PBMC cultures to induce B9.9 cell proliferation as well as p23-induced ISC formation in intact PBMC cultures. Fc region fragments induce both monocytes and T cells to produce IL-6. Taken together, these results indicate that IL-6 is produced in Fc region-stimulated PBMC cultures and is involved in B cell activation by these activators.

Adult↗
PubMed1990

C5a-mediated release of interleukin 6 by human monocytes.

Recombinant human C5a (rC5a) was assessed for its ability to induce interleukin 6 (IL-6) production in human peripheral blood-derived mononuclear cell (PBMC) cultures. rC5a was observed to induce IL-6 production as measured by hybridoma growth promotion (B9.9 assay) and human B cell differentiation (SKW6.4 assay). Optimal IL-6 production was obtained after 24 hr stimulation with 0.1-0.5 micrograms/ml rC5a. In addition, natural human C5ades Arg and natural porcine C5a were able to induce a similar level of IL-6. The observed IL-6 activity appeared not to be due to endotoxin contamination since heat treatment (100 degrees C/15 min) inhibited rC5a induction of IL-6. The rC5a stimulation also induced an increase in steady-state IL-6 mRNA as determined by Northern blot analysis. Pretreatment of PBMC with leucine-methyl ester to deplete monocytes reduced the rC5a-induced IL-6 production to background levels. In addition, stimulation of purified T cell preparations with rC5a produced little IL-6 activity, suggesting that monocytes are the major source of IL-6 in this system. These results suggest that the inflammatory and immunoregulatory activities of C5a may in part be due to the stimulation of IL-6 release, a cytokine which possesses potent pleiotropic functions.

Complement C5a↗
PubMed1990

Suppression of human B lymphocyte activation by beta-endorphin.

The effects of beta-endorphin (beta-E) and contained peptides were investigated for their ability to regulate Staphylococcus aureus (SAC)-induced immunoglobulin secretion by human B lymphocytes. Co-culture of beta-E with SAC-stimulated peripheral blood-derived mononuclear cells, under serum-containing or serum-free conditions, resulted in a dose-dependent inhibition of immunoglobulin-secreting cell (ISC) formation. When the same cultures were assessed for class-specific Ig formation it was found that IgG-ISC were suppressed to a greater extent that IgA-ISC or IgM-ISC. In contrast to these results, beta-E was found to be unable to suppress SAC-induced lymphocyte proliferation. To map the suppressive activity associated with beta-E, truncated peptides based on the beta-E sequence were assessed for biological activity. The results indicated that peptides containing the N-terminal region of beta-E suppressed ISC formation. Moreover, methionine-enkephalin (beta-E 61-65) was found to be effective in suppressing ISC formation. beta-E-mediated suppression of IgG-specific ISC formation appears to involve classical receptor-ligand interaction as evidenced by the ability of naloxone to block suppression of ISC formation.

Adult↗
PubMed1989

Induction of human B cell differentiation by Fc region activators. I. Identification of an active tetrapeptide.

Addition of pFc' fragments, composed of residues 334 to 446 in the Fc region of human IgG1, to cultures of human peripheral blood mononuclear cells resulted in the induction of Ig-secreting cells (ISC). Intact IgG1 and F(ab')2 fragments were inactive. The synthetic peptide p23, representing residues 335 to 357, retained the ISC-inducing property of pFc' fragments. The ISC response to p23 exhibited the isotype pattern IgMSC greater than IgGSC greater than or equal to IgASC. Results from cell depletion experiments revealed that the B cell response to p23 was T cell dependent but relatively monocyte independent. Cell proliferation was not increased in p23-stimulated PBMC cultures. Overlapping synthetic peptides based on the sequence of p23 were used to localize the active site in this molecule. These studies revealed that LPPSR (residues 351 to 355) was the sequence responsible for the ISC-inducing property of p23; however, expression of activity by this pentapeptide sequence could be dampened by N-flanking sequences. Finally, residue-deleted analogs of LPPSR were used to determine that LPPS was the minimum sequence retaining activity. Collectively, these data suggest that the fragmentation of IgG results in the expression of a tetrapeptide sequence with lymphocyte-stimulating properties.

Amino Acid Sequence↗
PubMed1989

Roentgenographic measurement of pedicle screw penetration.

Potential complications due to pedicle screw penetration of the anterior cortex include injury to vascular, visceral, ureteral, sympathetic, and neural structures. This study examined the accuracy of lateral roentgenographic techniques in determining actual screw penetration in vertebral levels T12 through S1 of ten unilateral sets of pedicles in five anatomic specimens. A true lateral roentgenogram alone was inaccurate for determining the penetration of the anterior cortex by a pedicle screw. The greatest discrepancy between roentgenographically apparent and actual screw penetration was found at the L4 and L5 levels. Deviation from a true lateral roentgenographic axis resulted in the most pronounced change in roentgenographically apparent screw penetration at L4 and L5. The roentgenographic axes resulting in the closest approximation of actual screw penetrations were 5 degrees and 10 degrees above the true lateral axis for the T12-L3 and the L4-S1 levels, respectively. At 50% apparent penetration, the screw may be safely assumed to not be penetrating the anterior cortex using a true lateral roentgenogram. At 80% apparent penetration, 30% and 10% probabilities of actual screw penetration of the anterior cortex exist at L4 and L5, respectively. At 100% apparent penetration, there is an almost 100% probability that the screw is actually protruding through the anterior cortex.

Biomechanical Phenomena↗
PubMed1988

Induction of IL-1 secretion from human monocytes by Fc region subfragments of human IgG1.

Peripheral blood-derived human monocytes and the murine P388D1-monocytes-like cell line are induced to secrete IL-1 when stimulated with Fc region but not F(ab) region subfragments obtained from the cleavage of human IgG1 with papain or pepsin. The portion of the Fc region of IgG1 responsible for stimulation of IL-1 secretion appears to be located within the C gamma 3 domain of the molecule. This hypothesis is supported by the observation that the biologically active pepsin-derived pFc' subfragment is located within the C gamma 3 domain and the long-term papain digests containing predominately Fc' are also active. In contrast, short term papain digests containing mostly intact Fc fragments were found to be unable to induce IL-1 secretion.

Animals↗
PubMed1987

Identification of a lymphocyte-activating pentapeptide sequence in the Fc region of human IgG1.

The synthetic peptide p23, representing residues 335 to 357 in the Fc region of human IgG1, was previously shown to induce Ig secretion in murine spleen cell cultures. In this report, overlapping peptides based on the sequence of p23 were synthesized to further map the active site in this molecule. The results from these studies indicate that leu-pro-pro-ser-arg (residues 351 to 355) retained the B cell differentiation-inducing properties of p23; however, expression of activity by this sequence was markedly influenced by N-flanking sequences. By using T cell-depleted spleen cell cultures, it was determined that at least two signals are required for p23-induced Ig secretion: one supplied by p23 directly and one supplied by a T cell-replacing factor present in p23-conditioned spleen cell supernatants. Both signals were mapped into the sequence leu-pro-pro-ser-arg. However, the latter signal, but not the former signal, again appeared to be influenced by sequences proximal to the active site. These data indicate that although the leu-pro-pro-ser-arg sequence is able to provide both required signals for p23-induced Ig secretion in spleen cell cultures, there may be subtle differences in how the cell types involved in this response interact with and/or are activated by this sequence.

Amino Acid Sequence↗
PubMed1987

Modulation of the induction and circumvention of immunological tolerance to human gamma-globulin by interleukin 1.

As with agents capable of causing the release of IL 1, IL 1 itself is capable of modulating certain tolerance-inducing events. Under the condition used in the present study, it previously has been firmly established that injection of A/J mice with DHGG induces a state of antigen-specific tolerance in both T helper (Th) and B cells. The tolerance in the B cell is of long duration, whereas that in the B cell is of shorter duration. Recombinant IL 1 (rIL 1) given shortly after the tolerogen DHGG results in the inhibition of the induction of tolerance resulting in antibody production. The induction of tolerance is inhibited at both its antigen-specific Th cell and B cell levels, although the latter may be caused by the former. The inhibition of the induction of tolerance by rIL 1 is not correlated to the generation of antigen-specific T suppressor cells. IL 1 mimics lipopolysaccharide and 8-bromoguanosine, which generate IL 1 production, in its ability to interfere with the in vivo induction of tolerance. However, in contrast to these latter mitogens which cause both terminal differentiation of B cells and IL 1 production, IL 1 itself does not cause in vivo circumvention of long-term tolerant Th cells in the presence of competent B cells and antigen. These latter findings suggest that a signal(s) in addition to those delivered by IL 1 is required for activation of the B cell compartment recovering from tolerance to antibody production. AHGG (immunogen) is a potent generator of IL 1 release, whereas DHGG has no effect on IL 1 release from macrophages and AHGG inhibits the induction of tolerance by DHGG. These latter results suggest that the lack of an IL 1 signal may be responsible for the deliverance of a tolerogenic rather than an immunogenic signal to the Th cell.

Animals↗
PubMed1987

The role of prostaglandins in C3a-mediated suppression of human in vitro polyclonal antibody responses.

Suppression of polyclonal antibody responses in human peripheral blood mononuclear cell cultures by human C3a appears to involve the release of endogenous prostaglandins from monocytes. C3a was found, under the experimental conditions employed, to activate the cyclooxygenase pathway of arachidonic acid metabolism with the release of large amounts of the prostaglandin E2 species. Suppression of the protein A-induced polyclonal antibody response by C3a is abrogated by the prostaglandin synthesis inhibitor indomethacin. In addition, physiologic amounts of exogenous PGE2 were able to inhibit polyclonal antibody secretion in a manner similar to the suppression observed when C3a was added to culture. These results suggest that C3a-induced release of prostaglandins could be a major element in immunosuppression induced by C3a.

Antibody Formation↗
PubMed1986

Antagonistic regulatory properties of the Fc region of immunoglobulin.

Coculture of human peripheral blood mononuclear cells with Fc fragments of human IgG, or the synthetic Fc region-derived peptide, p23, results in the release of oxidative products of arachidonic acid. Prostaglandin E was the major arachidonic acid metabolite found in the culture supernatants. Induction of polyclonal antibody production by Fc fragments and p23 is influenced by the concomitant production of prostaglandin E in culture. Addition of prostaglandin synthetase inhibitors, indomethacin and aspirin, to human peripheral blood mononuclear cell cultures resulted in a significant increase in the amount of polyclonal antibody produced. Moreover, addition of exogenous prostaglandin E to these cultures abrogated the ability of indomethacin to enhance Fc fragment-induced polyclonal antibody production. These results suggest that Fc fragments possess bifunctional immunoregulatory properties.

Adult↗
PubMed1986

Modulation of the immune response by anaphylatoxins.

Bioactive C3a and C5a fragments derived from the human complement compounds C3 and C5, respectively, possess immunoregulatory activities. C3a and C5a differentially influence in vitro immune function. C3a was found to be a potent suppressor of antigen-specific and polyclonal antibody responses. In contrast, C3a was unable to suppress antigen-or mitogen-induced B and T cell proliferation. Analyses of synthetic peptides based on the sequences of C3a revealed that the carboxy-terminal region of the molecule is responsible for immunosuppression. C3a-mediated suppression occurs through the activation of a nonspecific suppressor T cell pathway. In contrast to the results obtained with C3a, C5a was found to augment both in vitro humoral and cell-mediated immune responses. Regulation of immune function by complement components may form part of an in vitro nonspecific immunoregulatory network.

Adjuvants, Immunologic↗
PubMed1986

Lymphocyte activation by the Fc region of immunoglobulins.

The Fc region of Ig is required for numerous biological effector functions which include: opsonization, anaphylaxis, C fixation, catabolism of the Ig molecule, FcR binding, and immune regulation. To this latter point, the cellular and subcellular events involved in immune regulation by IC and Fc fragments of Ig have been the focus of numerous investigations. Characterization of cyanogen bromide cleavage fragments from a human IgG1 myeloma protein indicates that one biologically-active site is found in residues 335-357 of the CH3 domain of the molecule. Synthesis of the biologically-active region resulted in a peptide, termed p23, which stimulates mouse and human B cells to secrete polyclonal Ig and activates AA metabolic pathways. In contrast to these findings, p23 is unable to induce B cell proliferation or IL-1 secretion from macrophages. Analysis of data obtained with overlapping peptides, based on p23, suggests that the minimal active sequence needed for B cell differentiation is leu-pro-pro-ser-arg (residues 351-355). In contrast, only p23 or p23 minus the carboxyterminal glu356 and glu357 were able to induce PGE release. Release of biologically-active peptides derived from the Fc region of Ig into the cellular microenvironment may form the nucleus of a nonspecific in vivo immunoregulatory network. The specificity of peptide regulatory activities could reside in their effectiveness at high concentrations in the cellular microenvironment. The interaction of Fc region peptides with receptors on B cells, T cells, and macrophages/monocytes could result in a dynamic control of immune reactivity.

Amino Acid Sequence↗
PubMed1985

Binding and processing of immunostimulatory Fc gamma 1 fragments by the murine macrophage cell line P388D1.

Previous data from this laboratory indicated that human Fc gamma fragments induce murine B cells to proliferate and that the induction is macrophage-dependent. To further investigate the role of macrophages in this phenomenon, biologically active Fc gamma fragments from a human IgG1 myeloma protein and the murine macrophage-like cell line P388D1 were utilized. Fc gamma 1 fragments bound specifically and to a single class of receptor on P388D1 cells with a Ka value of 4 X 10(6) M-1 and to approximately 2.4 X 10(5) binding sites/cell. The binding was not effectively inhibited by two immunostimulatory Fc gamma 1 subfragments that were macrophage independent, i.e., pFc' fragments approximating the C gamma 3 domain of IgG1 and synthetic peptides representing residues 335-357 in IgG1. P388D1 cells were able to process Fc gamma 1 fragments but not intact IgG1 into subfragments that were able to induce lymphocyte proliferation in the absence of macrophages. The processing was rapid and resulted in active subfragments of several size classes. These findings not only further document the molecular and cellular events in these systems but underscore the usefulness of the P388D1 cell line in future studies on Fc fragment-induced lymphocyte regulation.

Animals↗
PubMed1985

Human C3a-mediated suppression of the immune response. II. Suppression of human in vitro polyclonal antibody responses occurs through the generation of nonspecific OKT8+ suppressor T cells.

C3a-mediated suppression of Ig secretion in human PBL cultures occurs through the activation of suppressor T cells. Incubation of T cell-enriched populations derived from peripheral blood or tonsil results in the activation of nonspecific OKT3+8+ suppressor T cells capable of inhibiting Fc fragment-induced Ig secretion in fresh autologous PBL cultures. Generation of OKT8+ suppressor T cells by C3a requires the interaction of T cells, adherent cells, and C3a. Activation of the suppressor-T-cell pathway is initiated early in culture. Incubation of the T-cell-enriched populations with C3a for 0.5 hr results in functional, transferable suppressor cells. Maximum suppression was achieved when C3a was allowed to interact with the cell population for 1-2 hr.

Antibody Formation↗
PubMed1985

Bifunctional lymphocyte regulation by human Fc gamma fragments and a synthetic peptide, p23, derived from the Fc region.

Fc fragments of human IgG1 and the synthetic peptide, p23, representing residues 335-357 in the CH3 domain of IgG1 were able to increase levels of secreted Ig in murine spleen cell cultures. B cell activation by Fc gamma fragments was macrophage- and T cell-dependent whereas activation by p23 was only T cell-dependent. Induction of Ig secretion by both stimulators was influenced by endogenous oxidative products of arachidonate, as evidenced by the augmentation of Ig levels in cell cultures treated with indomethacin (IM), a prostaglandin (PG) synthetase inhibitor. Both Fc gamma fragments and p23 were able to induce the release of PGE from splenic adherent macrophages and, in the former case, the release was inhibited by either IM or aspirin. Moreover, addition of either exogenous PGE1 or PGE2 reduced the levels of secreted Ig in Fc gamma fragment- or p23-stimulated cell cultures. These data suggest that B cell activation by Fc gamma fragments is influenced by the concomitant induction of suppressive PG.

Animals↗