Stephan E. Mergenhagen

Bone Resorbing Activity in Supernatant Fluid from Cultured Human Peripheral Blood Leukocytes

A new soluble mediator was found in supernatant fluid from cultures of human peripheral blood leukocytes that were stimulated by phytohemagglutinin, or by antigenic material present in human dental plaque deposits. This soluble Jactor produced bone resorption in organ cultures of fetal rat bones as measured by increased release of calcium-45, and also increased the number of active osteoclasts.

Inflammatory and immunomodulatory roles of TGF-β

Transforming growth factors (TGFs) are small polypeptides that were initially defined by their ability to induce transformation of non-neoplastic cells in culture. However, it has become increasingly clear that TGFs are not restricted in function to promoting cell growth. One type of transforming growth factor, TGF-beta, is a multifunctional molecule which has unique and potent effects on many target cells and tissues. In this article, Sharon Wahl, Nancy McCartney-Francis and Stephan Mergenhagen focus on the evolving role of TGF-beta in regulating inflammation, immune responses and tissue repair.

Complement-Dependent Stimulation of Prostaglandin Synthesis and Bone Resorption

Complement-sufficient heterologous serum induced prostaglandin synthesis and resultant resorption in cultures of fetal rat long bones. Bone resorption was enhanced with unheated normal rabbit serum as compared to heated serum or serum from rabbits lacking the sixth component of complement (C6). Addition of functionally purified C6 restored resorptive activity in C6-deficient serum. Concentrations of prostaglandin E were increased in the culture media of bones incubated with complement-sufficient serum. The resorptive effects of active serum as well as the appearance of prostaglandin E in the media were inhibited by indomethacin.

Autocrine and paracrine regulation of astrocyte function by transforming growth factor-β

Recent evidence indicates that astrocytes have a wide range of functions, usually attributed to cells of the immune system, which are critical for maintaining a balanced homeostatic environment in the central nervous system (CNS). Moreover, these cells are known to participate in inflammatory events within the CNS by secreting cytokines such as transforming growth factor-beta (TGF-beta). In this study we have investigated the ability of TGF-beta to influence astrocyte functions. TGF-beta 1 mRNA is constitutively expressed by astrocytes in vitro, and when cultures are stimulated with exogenous TGF-beta 1 an increase in the expression of this mRNA can be shown, suggesting both autocrine and paracrine regulation. In in vitro assays, TGF-beta 1 is chemotactic for astrocytes in a dose-dependent fashion and inhibits astrocyte proliferation. These results indicating signal transduction by TGF-beta 1-prompted studies to explore receptor-ligand interactions on isolated astrocyte populations. In a receptor binding assay, we demonstrate that astrocytes appear to express three distinct TGF-beta receptor subtypes with nearly 10,000 receptors per cell. Thus, TGF-beta may play an important role in regulating astrocyte functions pivotal to the evolution of intracerebral immune responses including recruitment and activation of glial cells at local inflammatory sites within the CNS.

Adhesion molecules as regulators of mast-cell and basophil function

Basophils and mast cells play a role both in immediate allergic reactions and in inflammation. Both types of cells have surface adhesion receptors that can mediate binding to other cells and to extracellular matrix glycoproteins. Here Majed Hamawy and colleagues discuss the importance of these adhesion molecules in regulating basophil and mast-cell functions.

Significance of complement to the mechanism of action of endotoxin.

Bacterial endotoxins are derived from the outer membrane of the complex cell wall of gram negative bacteria (Mergenhagen et al., 1966; Bladen et al., 1967) and are macromolecular structures containing polysaccharide, phospholipid, and small quantities of protein. Over the years much of the interest in bacterial endotoxins (lipopolysaccharides) has arisen because of the diversity of physiopathological and immunological effects these products have on the host. The biochemist has largely been concerned with the chemical and molecular basis for endotoxin action while the immunobiologist has tried to relate biological activity to the well-established fact that endotoxins are potent antigens and may give rise to some as yet ill-defined forms of hypersensitivity phenomena. Several recent symposia and reviews pertaining to the historical, immunobiological, and chemical interests of bacterial endotoxins have been compiled (Landy and Braun, 1964; Zweifach and Janoff, 1965; Nowotny, 1966; Luderitz et al., 1968; Neter, 1969) and it is out of the scope of this discussion to reiterate what has already been well documented in the literature except where certain of these references have a direct bearing on the subject at hand.

Protein tyrosine phosphorylation as a mechanism of signalling in mast cells and basophils

Tyrosine phosphorylation of proteins is a mechanism of signalling for different receptors and is important for cell growth and differentiation. Mast cells and basophils are secretory cells that play a role in inflammatory and immediate allergic reactions. The activation/aggregation of different surface receptors on these cells induces tyrosine phosphorylation of proteins. Because these signals are essential for the function of basophils and mast cells, characterizing these pathways could provide methods to specifically regulate the function of these cells. Here we discuss the signals generated by three receptors: the high affinity IgE receptor (Fc epsilon RI) the growth factor receptor, Kit, and integrins.

ELECTRON MICROSCOPIC LOCALIZATION OF ENDOTOXIC LIPOPOLYSACCHARIDE IN GRAM‐NEGAGIVE ORGANISMS

Endotoxicity and 0-antigenic specificity has been ascribed to the cell-walls of Gram-negative bacteria. Chemically, the cell walls of Gram-negative bacteria have been separated into an outer lipoprotein coat soluble in phenol, which is separated by a less dense layer from an inner mucopolypeptide layer termed the “R layer” which appeared dense in the electron microscope (Weidel et al., 1960). This latter layer contained the polysaccharide-lipid complex which was water-soluble after phenol extraction of cells, and was thought to be the site of endotoxicity. A phenol-water extract of a human oral strain of a Gram-negative, anaerobic coccus (Veillonella paruula) exhibited biological and immunological activities characteristic of somatic 0-lipopolysaccharides or endotoxins (Mergenhagen et al., 1961; Mergenhagen and Varah, 1963; Mergenhagen, 1965). This high-molecular-weight endotoxin was composed chiefly of lipid bound to a polysaccharide whose monosaccharide constituents were identified as glucose, glucosamine, galactosamine, and methyl pentose. In an electron microscopic investigation of this endotoxin and of the ultrastructure of V. paruula, results were obtained which suggested a morphological correlation of the outer membrane of the cell with particles observed in phenol-water extracts (endotoxin) (Bladen and Mergenhagen, 1964). When extracted with phenol, the outer membrane was removed and the cell retained its shape, owing to an inner solid membrane, which was sensitive to lysozyme. The results of the aforementioned study are summarized in this report in addition to a recent collaborative effort on the use of ferritin-conjugated rabbit anti-lipopolysaccharide globulins to localize endotoxic lipopolysaccharide in this organism.

Thymocyte Activating Factor(s) in Human Gingival Fluids

Human gingival fluid contains a low-molecular-weight factor (10,000 to 25,000) which enhances the proliferation of murine thymocytes in the presence of suboptimal doses of mitogen. Although the gingival fluid has no Interleukin 2 (T cell growth factor) activity, as indicated by its inability to induce proliferation of an IL 2 dependent lymphocytic cell line, it is directly mitogenic for dermal fibroblasts. These studies suggest that the thymocyte and fibroblast growth-promoting properties of human gingival fluid may have important functions in regulating inflammatory responses in the human periodontal tissues.

Inflammation and Herpes Simplex Virus: Release of a Chemotaxis-Generating Factor from Infected Cells

Infection of primary rabbit kidney cells with herpes simplex virus leads to the release of a cell factor or factors that upon incubation with serum results in the cleavage of the fifth component, C5, of complement. The product of this cleavage, C5a, is chemotactic for polymorphonuclear leukocytes and could be responsible for the accumulation of these cells at the site of herpetic lesions.