Significant Procoagulant Activity Research Articles

Immunohistological analysis of serial biopsies taken during human renal allograft rejection. Changing profile of infiltrating cells and activation of the coagulation system.

This immunohistological study investigated two aspects of the mechanisms underlying human renal allograft rejection. First, because rejection is a dynamic, complex process, we sought to delineate any changes in the types of cells mediating graft destruction by evaluating the cellular infiltrates in sequential renal biopsies from 14 patients with rejection. Second, because macrophage accumulation and fibrin deposition are major features of kidney rejection, the membrane characteristics of intragraft macrophages were analyzed to determine whether these cells could indeed cause the fibrin deposition frequently observed. Thirty-six biopsies, performed for assessment of renal failure posttransplantation (post-Tx), were studied using a panel of monoclonal antibodies and a 4-layer immunoperoxidase technique. Biopsies were divided into 3 groups depending upon the time post-Tx. Comparison of biopsies taken on days 2-3 post-Tx with those taken either at days 10-12, or later than 30 days, showed similar proportions of T cells, T cell subsets, B cells and macrophages. By contrast, the proportion of natural killer (NK) cells was significantly increased at days 2-3 (P less than .01), and the proportion of activated T cells bearing interleukin-2 receptors was significantly increased at days 10-12 (P less than .01). Granulocytes were restricted to biopsies that displayed areas of infarction, regardless of the time at which this occurred. In addition, various proportions of intragraft macrophages exhibited the membrane phenotype of activated macrophages, as a result of their expression of the procoagulant molecule termed human-tissue-factor--related antigen (HTF:RAg). The proportion of graft macrophages exhibiting HTF:RAg was significantly increased in biopsies on days 10-12 (P less than .05) compared with biopsies on days 3-4, and remained elevated thereafter. Interstitial and perivascular collections of HTF:RAg+ macrophages were closely associated with fibrin deposits and, in two cases, mononuclear cells harvested from rejected grafts were shown to contain significant procoagulant activity in vitro. These studies demonstrate a major temporal variation in the types of cells contributing to human kidney rejection.(ABSTRACT TRUNCATED AT 400 WORDS)

Procoagulant activity of human mononuclear leukocytes: dissociation of the effect of mitogens on procoagulant activity and mitogen-stimulated lymphocyte proliferation.

The role of mononuclear cells in generating procoagulant activity was examined by incubating Ficoll-Hypaque-separated mononuclear leukocytes with or without mitogens (phytohemagglutinin, pokeweed mitogen, and concanavalin A). The procoagulant activity was assayed by a modification of a one-stage plasma recalcification time. Significant procoagulant activity developed after 24 hr incubation and was dose dependent; mitogens alone had no effect on the clotting time. The increase in activity was paralleled by the increase in tritiated thymidine incorporation into replication DNA. However, mitomycin C had little inhibitory effect on the development of procoagulant activity, whereas thymidine incorporation was inhibited. The major procoagulant activity was associated with intact cells and not the conditioned supernatant. The removal of adherent mononuclear cells (mostly monocytes) by polystyrene bead columns abolished the procoagulant activity, whereas purification of mononuclear leukocyte populations for monocytes markedly increased the activity as compared to purified lymphocytes. The procoagulant activity was shown to act by the extrinsic limb of the coagulation sequence because of substitution factor VII-deficient plasma for normal plasma resulted in marked depression of procoagulant activity, whereas factor VIII-deficient plasma resulted in a clotting time only minimally longer then normal plasma. Thus, although procoagulant activity in cultures of mononuclear cells is stimulated by the mitogen reagent, these studies suggest that the activity may not be the result of the mitogenic effect on lymphocytes per se. Whether it is a direct effect of the mitogen on the adherent cell or is an effect of a contaminant of the mitogen reagent, such as endotoxin, remains to be determined.

Endotoxin-induced cytotoxicity and procoagulant activity of mouse bone marrow cells

1. Bone marrow cells of mouse given endotoxin (LPS-cells) accerelated the plasma recalcification time (RCT) and partial thromboplastin time (PTT) of mouse or rabbit plasma. PTT was more sensitive than RCT. 2. A significant procoagulant activity of LPS-cells was demonstrated as early as 4hr and the peak was found 8-18hr after endotoxin. This peak was coincided with those of the cytotoxicity and the decrease of nucleated cell counts in marrow. 3. Either the procoagulant activity of LPS-cells of the mouse or the activity of mouse brain thromboplastin (MBT) was more marked in mouse plasma than in rabbit plasma. There would be a species specificity between the two animals, as to coagulation. 4. The two regression lines of the PTT on either the number of LPS-cells or the dose of MBT were nearly parallel. 5. Dose response regression of cytotoxicity or generation of procoagulant activity on concentration of endotoxin injected was significant. Cytotoxicity and procoagulant activity of LPS-cells were demonstrated even by injection of as little as 5μg endotoxin. 6. There existed a definite correlation between the cytotoxicity and procoagulant activity of LPS-cells (n=20, r=-0.8452, p<0.001).These findings suggested that procoagulant activity of LPS-cells is shown to be tissue thromboplastin in nature, and the migrated-cells in circulation play an important role in blood coagulation of endotoxicosis.