Activation of an interleukin-1-responsive T-cell lymphoma by fixed P388D1 macrophages and an antibody against the Ag:MHC T-cell receptor

The expression of cytokine activity by fracture callus

Cytokines, a group of proteins known to regulate hemopoietic and immune functions, are also involved in inflammation, angiogenesis, and bone and cartilage metabolism. Since all of these processes occur following bone injury, or are known to contribute to wound repair mechanisms, this investigation sought to test the hypothesis that cytokines are involved in fracture healing. Two sets of 60 male Sprague-Dawley rats underwent the production of standard closed femoral fractures. The animals were then euthanized in groups of 15 on days 3, 7, 14, and 21 postfracture. A separate control group was also used for the harvesting of intact unfractured bone. At the time of euthanasia, calluses or bone specimens were explanted to organ culture and treated with either media alone or media containing the inducing agents lipopolysaccharide or concanavalin A. A titration of conditioned medium from these cultures was then added to factor-dependent clonal cell lines that are known to be specifically responsive to interleukin-1, interleukin-6, granulocyte-macrophage colony stimulating factor or macrophage-colony stimulating factor. To confirm the identities of each of these cytokines, neutralizing antibody studies were performed. The results showed that interleukin-1 is expressed at very low constitutive levels throughout the period of fracture healing but can be induced to high activities in the early inflammatory phase (day 3). Granulocyte-macrophage colony stimulating factor showed no constitutive activity but could also be induced to high activities with lipopolysaccharide. The ability of these two cytokines to be induced declined progressively as fracture healing proceeded. Interleukin-6 showed high constitutive activity early in the healing process (day 3), and treatment with inducing agent did not increase the activity of this cytokine at this timepoint. Lipopolysaccharide did increase interleukin-6 activity in day 7 and 14 fracture calluses. Although macrophage-colony stimulating factor is thought to be involved in a variety of metabolic bone conditions, it could not be detected or induced from any of the callus samples. Moreover, none of the samples of unfractured bone showed constitutive or inducible activities for any of these cytokines. A separate experiment in which calluses and samples of unfractured bone from similar cultures were examined histologically and tested for DNA or protein synthesis at two timepoints in the culture period (days 1 and 4) showed that tissue viability was maintained. Thus the inability to detect macrophage colony-stimulating factor in fracture callus or any cytokine activity in unfractured bones was not due to cell death.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological activity of recombinant murine interleukin-6 in interleukin-1 T cell assays

Interleukin-6 (also called B cell stimulatory factor 2, hepatocyte activating factor, interferon-beta 2) has been shown to have effects on various lineages of hemopoietic cells. Some of its activities appear to overlap those of interleukin-1. In particular, recombinant murine IL-6 induced proliferation of phytohemagglutinin-activated thymocytes, an assay widely used to detect IL-1. In this report, we compared several features of IL-1 and IL-6 dependent thymocyte proliferation. The results indicate that IL-2 is the major second mediator of both IL-1 and IL-6 dependent proliferation. Finally, we tested whether IL-6 would also have activity in other T cell-based IL-1 assays using the T cell lymphoma LBRM33 1A5 and the T cell clone D10-G4.1. IL-6 had no activity in the latter two assays. These results indicate that IL-1 assays using LBRM33 1A5 and D10-G4.1 selectively detect Il-1, and are more specific assays for the detection of IL-1 in samples that may also contain IL-6.

Inhibition of T-cell antigen receptor-mediated transmembrane signaling by protein kinase C activation

The murine T-lymphoma cell line LBRM-33 is known to require synergistic signals delivered through the antigen receptor (Ti-CD3) complex, together with interleukin 1 (IL-1), for activation of IL-2 gene expression and IL-2 production. Although 12-O-tetradecanoylphorbol-13-acetate (TPA) was capable of replacing IL-1 as an activating stimulus under certain conditions, biologic studies indicated that TPA failed to synergize with Ti-CD3-dependent stimuli under conditions in which IL-1 was clearly active. Acute exposure to TPA and other active phorbol esters resulted in a concentration-dependent inhibition of the increases in phosphoinositide hydrolysis and intracellular free Ca2+ concentration stimulated by phytohemagglutinin or anti-Ti antibodies. TPA treatment induced no direct alteration of phospholipase C enzymatic activities in LBRM-33 cells. In contrast, both Ti-CD3 cross-linkage and TPA rapidly stimulated the phosphorylation of identical CD3 complex polypeptides, presumably via activation of protein kinase C. Exposure of LBRM-33 cells to TPA resulted in a time-dependent, partial down-regulation of surface Ti-CD3 expression. Thus, TPA treatment inhibited the responsiveness of LBRM-33 cells to Ti-CD3-dependent stimuli by inducing an early desensitization of Ti-CD3 receptors, followed by a decrease in membrane receptor expression. These studies indicate that phorbol esters deliver bidirectional signals that both inhibit Ti-CD3-dependent phosphoinositide hydrolysis and augment IL-2 production in LBRM-33 cells.

Inhibition of T-cell antigen receptor-mediated transmembrane signaling by protein kinase C activation

The murine T-lymphoma cell line LBRM-33 is known to require synergistic signals delivered through the antigen receptor (Ti-CD3) complex, together with interleukin 1 (IL-1), for activation of IL-2 gene expression and IL-2 production. Although 12-O-tetradecanoylphorbol-13-acetate (TPA) was capable of replacing IL-1 as an activating stimulus under certain conditions, biologic studies indicated that TPA failed to synergize with Ti-CD3-dependent stimuli under conditions in which IL-1 was clearly active. Acute exposure to TPA and other active phorbol esters resulted in a concentration-dependent inhibition of the increases in phosphoinositide hydrolysis and intracellular free Ca2+ concentration stimulated by phytohemagglutinin or anti-Ti antibodies. TPA treatment induced no direct alteration of phospholipase C enzymatic activities in LBRM-33 cells. In contrast, both Ti-CD3 cross-linkage and TPA rapidly stimulated the phosphorylation of identical CD3 complex polypeptides, presumably via activation of protein kinase C. Exposure of LBRM-33 cells to TPA resulted in a time-dependent, partial down-regulation of surface Ti-CD3 expression. Thus, TPA treatment inhibited the responsiveness of LBRM-33 cells to Ti-CD3-dependent stimuli by inducing an early desensitization of Ti-CD3 receptors, followed by a decrease in membrane receptor expression. These studies indicate that phorbol esters deliver bidirectional signals that both inhibit Ti-CD3-dependent phosphoinositide hydrolysis and augment IL-2 production in LBRM-33 cells.

Keratinocyte membrane-associated epidermal cell-derived thymocyte-activating factor (ETAF)

This study describes the association between secreted keratinocyte interleukin 1 (IL-1) and its presence on the keratinocyte cell surface. These properties were studied in normal and transformed human keratinocytes as well as in transformed murine keratinocytes. We will present evidence that the secretion of IL-1 by human and murine keratinocytes is associated with the presence of IL-1 on the keratinocyte membrane. In addition, although transformed murine keratinocytes secrete other cytokines, namely keratinocyte T-cell growth factor (KTGF) and IL-3, no KTGF or IL-3 activity can be demonstrated on the cell surface.

Expression in Escherichia coli of synthetic human interleukin-1 alpha genes encoding the processed active protein, mutant proteins, and beta-galactosidase fusion proteins

We have synthesized, cloned, and expressed the coding region for the C-terminal 159 amino acids (aa) of the human active interleukin polypeptide hormone IL-1 alpha. The sequence was assembled in stages and includes preferred Escherichia coli codons and unique restriction sites. The coding region was cloned on a multicopy plasmid vector adjacent to signals for transcription and translation that directed synthesis of 6% of total E. coli protein as IL-1 alpha. Active IL-1 alpha mutants that have a C-terminal additional eleven aa and that have N-terminal deletions of six and fourteen aa are described. Plasmids expressing beta-galactosidase fusion proteins with various parts of IL-1 alpha at their N-termini were constructed.