Induction of monocyte/macrophage procoagulants may occur as the result of activation of the cell-mediated immune (CMI) response.
Macrophage procoagulant inducing factor (MPIF), a soluble product of stimulated TDTH lymphocytes, may act together with two
monokines,
interleukin 1 and tumour
necrosis factor alpha, which induce
thromboplastin on endothelial cells, to initiate the
fibrin deposition which is a common feature of many diseases in which CMI plays a role. Murine MPIF is chemically distinct from a number of other well characterized
lymphokines in that the two major activities, MPIF alpha and MPIF beta are
heparin-
binding proteins with high isoelectric points. Fractions highly enriched for MPIF induced interstitial
fibrin deposition when injected intradermally. In addition, intense infiltration of polymorphonuclear leucocytes (PWN) and mononuclear cells was seen 4-24 h following
intradermal injection. In vitro experiments have confirmed that this lymphokine is a potent chemotactic agent for these cells. These results suggest that MPIF plays a central role in the expression of histopathological features of delayed-type
hypersensitivity reactions. Monocyte and macrophage procoagulants induced by MPIF would contribute significantly to the activation of coagulation which not only results in
fibrin deposition but also in the production of activated
serine proteases and fibrinopeptides which may potentiate an inflammatory response.