---start path.lec.04.04.97---- finishing up acute inflammation... we were discussing the hageman factor (XII) and the interactions of kinin, fibrinolytic, and coagulation systems. in severe, acute inflamm rxn, fibrinogen does get out of vessels and polymerizes into fibrin, due to increased vascular permeability. this CAN occur intravascularly as well, mainly along the heart valves eg mitral or aortic in particular - they can undergo severe inflammatory rxn caused by bacteria localizing there. you get excessive turbulence at the valve maybe due to anatomic abnormality, causing bacteria to localize there, ad produce toxin, and kill nearby cells, eg endothelial cells, allowing factor XII to be contacted by subendothelial collagen, activating the coagulation system inside the heart. you build up a fibrin/platelet thrombus onn the valve, and this is a very serious problem, esp in left heart - small thrombi can breakk off and become emboli in coronary arteries, brain, kidney, spleen and cause infarcts. assuming these emboli have bacteria in them, you can get say a brain abcess, kidney abcess, etc. yuck! white blood cells: primary cell type in acute infl rxn is neutrophil. how does neut responnd in acute infl rxn? how does it get out of blood vessels? the neuts marginate - migrate toward vessel wall, not stay in center of stream. they may "pavement" eg line up and roll along endothelium. they bind onto endo, then migrate out the gaps between the endothelial cells.it used to be a real enigma why they tend to adhere to endothelium. but we know now it's all mediated by adhesion molecules. endothelial cells undergo specific changes...in acute innfl resp, monocytes ad macrophages liberate IL1, TNF, often LPS is around...later, we see gIFN from lymphs...and these things upregulate adhesion mols on the endothelium. IL1 and TNF also upregulate adhesion mols on the neutrophils. what kind of adhesion mols are there? well, C5a also upregulates adhesion mols on neutrophils. if you look at it as time course of events during acute infl resp...thrombin and histamine act on endo in short acute phase, the the factors we just mentioned act for a longer period. so, in the short period, PAF and P-selectin are upregulated on the endothelial cells (Platelet activating factor and 'platelet' selectin. note that the lectin can bind very sugar rich ligands. doesn't only bind platelet). during the later phase, E-selectin and IL8 are upregulated by IL1 and TNF, so the endothelial cell liberates IL8, a neutrophil chemoattractant, and expresses surface E-selectin. rolling and margination of neutrophil is mainly mediated by selectin molecules. when it comes to firm adhesion of neutrophil, prior to emigrationn, that is mainly mediated by integrins. remember that selectins bind to carbohydrate rich molecules. they help the neutrophils stay marginated and stuff. LFA leukocyte function associated molecule is an integrin, and it binds to ICAM on the endothelium, and that binding will trigger emigration of the neutrophil. cancer/tumor cells...these also have adhesion molecules. so thinking about metastasis...it's also mediated by these adhesion molecules. you could try to regulate ability of these cells to migrate by changing or blocking some adhesion mols. ---- CHEMOKINES: new group of small polypeptide mols, produced by a number of diff cells in vicinity of acute infl rxn, called this b/c they have intense chemotactic affinity for certain WBCs. EG: IL8: made by monocytes, mphages, fibroblasts, keratinocytes...potent attractor of neutrophils. MCP1: monocyte chemoattractant protein, made by monos, mphages, fibroblasts and keratinocytes also...attracts and activates monocytes RANTES: made by T cells, acts like MCP1 Eotaxin: latest of these chemokines. has almost exclusive ability to attract eosinophils. are about 16 known chemokines, but these are the ones to know. ---- next question: what is importance of neutrophil in acute infl rxn and how do they function? totally beneficial? any neg effects? well... neutrophils phagocytize bacteria, esp when bacteria is opsonized by Ig mols. when bacteria enters phagosome, is big increase in O2 consumption by neutrophil (or macrophage), and then an oxidase liberates a superoxide ion which is reduced to H2O2, and then the phagosome fuses w/lysosome becoming a phagolysosome...myeloperoxidase will take a Cl- or an I- eg a halide and become say a hypochlorite HOCl- which is a very potent killer of bacteria. now, some bacteria have catalase. they break down the H2O2 so that you don't get interaction w/myeloperoxidase forming hypochlorite, so bacteria can live a lot longer. also neuts have endogenous catalase which does this to some extent. this is main oxygen dependent killing mechanism. the H2O2 myleoperoxidase halide killing system. but there are other killing ways.... oxygen independent: lactiferrin, lysozyme, bacteria permeability increasing protein (BPI), defencins - all can kill bacteria independent of O2. as neut phagocytizes, they release some oxygen radicals into the extracellular space, through the opening of phagosome. so some radicals and enzymes getout there and they kill more host cells, perpetuating the inflammatory rxn. in additionn, activated neutrophils are making leukotrienes and prostoglandins and stuff, some of which perpetuate the inflamm response. how long does extravascular neutrophil live? well, in bloodstream, neut half life about 10 hrs. realize they do not go back IN to the blood after they leave the vessel, ever. once they get in the tissue, they live only 24-48 hrs. then they will die. so, assume you've got an abcess. a lot of IL8 draws in a lot of neutrophils. they all die within 24-48hrs. so, this allows liberation of all these O2 metabolites and enzymes into the local area, and causes autodigestion...this is why you get PUS. pus is an accumulation of dead/dying neutrophils, plasma fluid, and dead and dying regional cells. the phagocytosis process isn't perfect, of course. consider someone w/low level of Ig, or complement...less opsonization, less effective phagocytosis. a patient with diabetes has less O2 consumptio, and poor glucose utilization, so phagolysosome function is very poor, so uncontrolled diabetics haveproblems with acute infl rxns. in cattle and dogs, there are LAD leukocyte adhesion deficiency syndromes. they are missing some adhesion molecules - mainly integrins - so they dono't get tight binding of neuts to endothelium, and don't get good extravasation, so animals can'nt fight infxn well b/c neuts don't leave blood vessels. could also have leukocyte oxidase deficiency causing chronic granulomatous inflammatory disease. here you can't use the oxygen metabolites correctly. slide: one or two things about PAF platelet activating factor. it activates platelets. it comes from almost all WBCs plus endothelial cells. it's produced whenever WBC or endothelial cells are activated or stimulated by cytokines or whatever. PAF causes platelet aggregation and binding to endothelium, causes platelet to secrete procoagulant chemicals, eg thromboxane; causes neutrophils to aggregate and adhere to endothelium, increases lysosomal enzyme release, increases metabolic activity of neut, increases chemotaxis; similar things to macro/monos - aggregation, adherence, icreased activity, etc. --- IL1/TNF complex - main source is activated macrophages. bacterial products, toxins, LPS, physical injury, cytokines, immune complexes all activate mphages. main effects of IL1/TNF: acute phase rxns, endothelial fx, fibroblast fx. acute phase rxns: fever (IL1/TNF acting on hypothalamic regulatory center), increased sleep, decreased appetite, increased acute phase proteins (one of earliest indicators of local or systemic acute infl rxn. rise in fibrinogen is often measured - good thing to look at in herbivores.), hemodynamic effects (shock), neutrophilia - good thing to look for in cats/dogs - there will be increased absolute neuts...and you will see a "left shift" meaning that the circulating neutrophils are immature - eg, increased numbers of band neutrophils - this indicates that bone marrow is pumping out immature neutrophils. this is good, shows you that bone marrow is responding.... endothelial effects: increased leukocyte adherence, increased PGI (prostacyclin) synthesis, increased PAF, increased procoagulant activity, decreased anticoagulant, increased IL1. fibroblast effects: increased proliferation, increased collagen synthesis, etc. stimulated by IL1. where do acute phase proteins come from? the liver. liver is triggered by IL1 and IL6. IL6 is multifunctional cytokine. as mphage is activated it makes IL1, TNF, IL6 and all those stimulate liver to make acute phase proteins including C reactive protein and mannose binding protein, which can trigger the complement pathway therefore playing part in inflammatory response. acute phase protein level peaks between 6-11 days... septic shock: a rather big thing. most of the time people discuss septic shock in relation to infxn with gram neg organisms eg E.Coli, et al. but still, you can get septic shock with accumulation of gram positive organisms as well. septic shock has a few key areas where it acts to bring on the deadly effects. it activates complement system, for one thing. this is done by LPS or endotoxin (same thing) of the gram negative organisms which have cell walls containing this substance. so, you generate anaphylatoxins this way, which have dramatic vascular effects as previously discussed. second thing - triggers mphages and monos to make IL1 and TNF which upregulate adhesion molecules. so end effect of LPS stimulating mphage to make IL1 and TNF is massive accumulation and adherence ofneutrophils in blood vessels. also PAF causes platelets to aggregate. you build up thrombi. blood coagulates, fibrin is deposited...the anaphylatoxins and effects of IL1 and TNF cause peripheral vasodilation, causing hypovolemic shock symptoms, and because of accumulation of neuts, plates, and fibrin in blood vessels you have DIC disseminated intravascular coagulation - basically tons of little tiny clots form all over the vasculature, and the clotting factors and platelets are all used up, and then you bleed to death. Once DIC reaches a certain point, it is irreversible. attempts have been made to tx w/anti TNF et al, but it doesn't really work so you can have primary infl rxn eg in GI tract, and gram neg organism will go to liver, b/c blood drains that way. there, kuypfer cells are activated, making TNF and IL1 which circulates and gets to the lung, and now you get activation and accumulation of neutrophils, and you can end up with ARDS - acute respiratory distress syndrome (eg like from hantavirus) which is a variant of septic shock. you see that the effect of the inflammation is in a totally separate organ system from the site of inflammation. from here, you can get MOSF - multiple organ system failure - due to less and less oxygenation occuring. you could have severe metritis or prostatitis causing ARDS or MOFS this way. so septic shock is a very important thing you should have a basic understanding of. ---end---