Lymphoid procoagulant response to bacterial endotoxin in the rat

Abstract

A number of species respond to bacterial endotoxin (lipopolysaccharide [LPS]) wherein cells of the monocyte-macrophage lineage are rapidly induced either directly or via T-cell collaboration to initiate the extrinsic coagulation protease pathway. This results in fibrin formation and deposition as weli as consumption of plasma coagulation proteins. It has been claimed that this cellular response, basic to the Shwartzman reaction, is lacking in rats and may account for the more limited severity of the Shwartzman reaction in this species. We examined the in vitro lymphoid procoagulant response in Fischer 344, Brown Norway, and Lewis rats. When peripheral blood mononuclear cells (PBM) were stimulated in vitro with LPS, a procoagulant activity (PCA) response was observed when assayed by acceleration of clotting of recalcified human or rat platelet-poor plasma. The response was rapid, with a maximum achieved at 4 h. PCA was not physically dissociated from viable PBM by 5 mM EDTA, which is consistent with the presence of an intrinsic plasma membrane initiator molecule rather than calcium-bound gamma-carboxylated glutamic acid-containing proteases. The induction of monocyte PCA was prevented by incubation of cells with cycloheximide or actinomycin D, implicating a new biosynthetic requirement. Cultivation of PBM with warfarin did not diminish the function of the effector PCA, nor did vitamin K augment the function of the endotoxin-induced PCA, indicating that the functional activity was not attributable to gamma-carboxylated glutamic acid-containing proteins. No inhibition of the cellular PCA molecule was produced by serine protease inhibitors. The LPS-induced PCA appeared to involve a tissue factor-like molecule since both factors X and VII were required in mediating PCA. Isolation of monocytes and T lymphocytes from LPS-stimulated PBM demonstrated that PCA was present in the monocyte-rich fraction. When isolated rat T lymphocytes and monocytes were separately exposed to LPS, PCA was not induced. In contrast, when the cells were combined, LPS induced PCA, indicating that the PCA response involved cellular collaboration between cells present in T lymphocyte and monocyte populations.

The role of tyrosine phosphorylation in lipopolysaccharide- and zymosan-induced procoagulant activity and tissue factor expression in macrophages

“…Clotting times were converted to milliunits of PCA by comparison with the clotting times of a rabbit brain thromboplastin standard in which 36 mg (dry weight) per ml was assigned a value of 100,000 mU of PCA. Results of previous studies have demonstrated that LPS-induced mouse macrophage PCA is only slightly less effective in shortening the clotting time of human plasma than in shortening the clotting time of mouse plasma (43). The induction of PCA from a baseline of 300 mU/10 6 macrophages to 2,800 mU/10 6 macrophages in cells stimulated by LPS alone represented a shortening of the clotting time from 70 to 52 s. The assay was used over the range of 10 to 10,000 mU of PCA, this range being linear with a normal plasma substrate.…”

Pasteurella haemolytica A1 and Bovine Respiratory Disease: Pathogenesis

“…Also, the induction of procoagulant activity in macrophages is lymphocyte-dependent. 164 The role of lymphocytes in the acute inflammatory response in bovine shipping fever is speculative. However, some interesting observations implicate their involvement.…”

Disparate mechanisms of induction of procoagulant activity by live and inactivated bacteria and viruses

“…Clotting times were converted to milliunits of PCA by comparison with a rabbit brain thromboplastin standard (Dade Division, American Hospital Supply, Miami, Fla.) in which 36 mg (dry weight) per ml was assigned a value of 100,000 mU of PCA. Results of previous studies have demonstrated that lipopolysaccharide-induced mouse monocyte PCA is only slightly less effective at shortening the clotting time of human plasma than at shortening the clotting time of mouse plasma (14). The induction of PCA from a base line of 20 mU/106 macrophages to 2,000 mU/106 macrophages in stimulated macrophages represented a shortening of the clotting time of 60 to 70 s. The assay was used over the range of 1 to 10,000 mU of PCA, with this range being linear with normal plasma substrate.…”