Macrophage Procoagulant Activity Research Articles

Endotoxin-induced T lymphocyte proliferation.

The lymphocyte response to endotoxin (LPS) has been attributed largely to the action of this agent as a polyclonal activator of B lymphocytes. In this study we found that a cloned murine interleukin 2-dependent cytotoxic T cell line, CT 6, proliferates in response to LPS, thus providing the first evidence that T cells can be stimulated directly by LPS. The response was dose and time dependent and was blocked by polymyxin B, an inhibitor of LPS-induced mitogenesis. The fact that this is a cloned T cell line, free of other potentially contaminating lymphoid cell types, precludes the possibility that this proliferation is due to contaminating B lymphocytes or is mediated by macrophage-derived products such as interleukin 1. Moreover, highly purified splenic T lymphocyte populations (purified by negative/positive selection or by a rigorous column purification procedure) contain a small subpopulation (approximately 3%) of T cells that proliferate in response to LPS. This population is missing in the endotoxin-hyporesponsive C3H/HeJ mouse. As was observed in the CT 6 line, proliferation of splenic T cells in response to LPS was inhibited by polymyxin B. Furthermore, treatment of LPS-stimulated T cells with anti-T cell antibodies plus complement blocks the uptake of 3H-thymidine by these cultures. Exogenous interleukin 1 failed to stimulate the T cell cultures comparably to LPS and therefore cannot account for the degree of stimulation observed. These findings support and extend previous findings that suggested a role for an endotoxin-sensitive T cell population in the induction of certain responses, such as LPS-induced adjuvanticity of the lymphocyte-dependent LPS induction of macrophage procoagulant activity.

Coordinate expression of macrophage procoagulant and fibrinolytic activity in vitro and in vivo.

Coordinate expression of macrophage procoagulant and fibrinolytic activity in vitro and in vivo.

Generation of procoagulant activity (PCA) by phorbol-esters-induced macrophages derived from a leukemic promyelocytic cell line (HL-60)

Normal human monocytes and macrophages, as well as leukemic promyelocytes, generate potent procoagulant activity (PCA) resembling thromboplastin. In the present study only mild PCA was detected in a leukemic promyelocytic cell line (HL-60) and in promyelocytic cells induced to differentiate into neutrophils by dimethylsulfoxide (DMSO). After exposure to 12-0-tetradecanoylphorbol-13-acetate (TPA), the leukemic promyelocytic cells assume characteristics specific to monocytes and macrophages. This differentiation was associated with potent PCA generation. No PCA was found in lymphoblasts and several lymphoid cell lines after exposure to TPA. The PCA in TPA-induced HL-60 cells resembles tissue thromboplastin and normal monocyte PCA in several aspects: (A) All three accelerate clotting through the extrinsic coagulation pathway; (B) all three are inhibited by concanavalin-A and protected by methyl-α-D-mannopyranoside, suggesting that the PCA contains carbohydrate moieties; (C) the PCA is located in the cell membrane. However, the mechanism of PCA generation in normal monocytes and in TPA-induced HL-60 cells differs in several aspects: (A) Endotoxin and phytohemagglutinin, which are potent stimuli of PCA generation in normal monocytes, have no effect on TPA-induced HL-60 cells; (B) HL-60 cells treated with TPA develop PCA before acquiring any other specific characteristic of monocyte or macrophages; (C) the development of PCA in TPA-induced macrophages is not dependent on cell adhesion or the presence of T cells. In spite of these differences, the production of PCA is additional evidence of the similarity between TPA-induced macrophages and normal human monocytes and macrophages. The HL-60 cells may provide a unique model for studying PCA generation in mononuclear cells.

A mechanism of migration inhibition in delayed-type hypersensitivity reactions. II. Lymphokines promote procoagulant activity of macrophages in vitro.

Although lymphokine supernatants had no procoagulant activity per se, guinea pig peritoneal exudate cells (PEC), incubated with lymphokine supernatants or with a lymphokine fraction of 35,000 to 50,000 daltons decreased the recalcification time of platelet-poor plasma. PEC from animals immunized with BCG or with ovalbumin and incubated with the corresponding antigen had increased procoagulant activity. Similar effects were observed with PEC incubated with endotoxin. The induction of procoagulant activity by the cells was accompanied by a concomitant decrease in their ability to respond to chemotactic agents and to migrate from capillary tubes. Separation of exudate cells by sedimentation velocity indicated that large macrophages had the highest degree of procoagulant activity after incubation with lymphokines. The clotting time of Factor IX-deficient plasma was decreased by lymphokine-treated macrophages, indicating that the extrinsic clotting sequence may be activated as a result of increased tissue factor on the treated cells. Heparin abolished the ability of lymphokines to inhibit macrophage migration.

Lymphocyte cooperation is required for amplification of macrophage procoagulant activity.

Murine splenic lymphoid cells have been shown to possess basal procoagulant activity. This activity was localized to most macrophages by assay of cell populations, as well as by a direct plaque assay that permitted identification of expressed procoagulant activity of individual viable cells as well as content. Both content and viable expression of procoagulant activity was markedly increased by exposure to bacterial lipopolysaccharide, reaching a maximum after 6 h. The quantitative increase in procoagulant activity content and viable expression was limited to the macrophage population. Separated populations of lymphocytes or macrophages could not be stimulated by lipopolysaccharide to increase procoagulant activity, whereas the addition of lymphocytes to macrophages at a 3-4:1 ratio maximally reconstituted the amplification of procoagulant activity. Further evidence of cellular collaboration followed from observation that only lymphocytes that had been exposed to lipopolysaccharide were capable of triggering the increase in macrophage procoagulant activity. This appears to represent a new form of lymphocyte-macrophage cooperation in an effector pathway that may participate in some forms of immunologic responses and contribute to the phenotypic features of certain immunologic tissue lesions.

Procoagulant activity of peritoneal leukocytes: effects of cortisone and endotoxin.

Procoagulant activity of peritoneal leukocytes from rabbits given cortisone acetate, endotoxin, and both materials was measured in studies designed to test the hypothesis that cortisone acetate prepares rabbits for the generalized Shwartzman reaction by enhancing leukocyte procoagulant activity. Two types of peritoneal leukocyte suspensions were examined: mixed granulocyte-macrophage suspensions and macrophage suspensions. In both types, procoagulant activity could be accounted for by the number of macrophages in the suspensions. Cortisone alone did not affect the procoagulant activity, whereas endotoxin increased the procoagulant activity. Suspensions from animals given both cortisone and endotoxin varied in activity depending upon cell composition. Granulocyte-macrophage suspensions had less apparent procoagulant activity than suspensions with endotoxin alone. In contrast, macrophage suspensions--particularly sonicated suspensions--had greater procoagulant activity than those with endotoxin alone. The ability of cortisone acetate to increase macrophage procoagulant activity after endotoxin could represent one mechanism whereby cortisone acetate prepares rabbits for the generalized Shwartzman reaction after endotoxin.