THE PLATELET AS AN INFLAMMATORY CELL RALPH L. NACHMAN, M.D. AND (BY INVITATION) MARGARET POLLEY, PH.D. NEW YORK
One of the earliest steps in the primary hemostatic defense mechanism involves the adhesion of circulating platelets to denuded subendothelial structures such as collagen, basement membrane, and microfibrils in the vicinity of a damaged endothelial surface. Collagen-activated platelets induce the release of intracellular constituents including ADP, serotonin and products of the arachidonate transformation pathway. The released ADP, thromboxane A2 and prostaglandin endoperoxides formed from arachidonate lead to the formation of a platelet aggregate which eventually plugs and seals off the disrupted vessel. It is now generally considered that this sequence of events contributes to the genesis and development of the white thrombus in human pathology and may play a signal role in the atherogenesis. This primary hemostatic response involving the platelet blood vessel wall reaction in mammals resembles to a significant extent the basic cellular defense mechanisms of more primitive forms such as invertebrates. Human platelets contain intracellular granules similar to the classical lysosomes of polymorphonuclear leukocytes' and contribute to the inflammatory response accompanying tissue injury by releasing constituents which may alter blood vessel reactivity. Platelets accumulate in vessels adjacent to inflammatory sites and interact with bacteria, viruses, and antigen-antibody complexes. Platelets and polymorphonuclear leukocytes have the same primitive phylogenetic ancestor and perform similar inflammatory functions although in different geographic settings. The platelet performs its functions in the intravascular compartment while the polymorphonuclear leukocyte performs its major functions in extravascular spaces. The primary hemostatic response involving the platelet blood vessel wall reaction in higher forms such as mammals appears to have retained a phylogenetic vestige of primitive leukocyte behavior. In this regard, it is useful to consider primary hemostasis as basically an inflammatory response and thus the platelet can be thought of as a special form of leukocyte (Table I). Several years ago it was demonstrated that platelets contribute to the inflammatory response accompanying tissue injury by releasing constitDepartment of Medicine, Cornell University Medical College, New York City. Supported by NIH grant (HL18828) and the Arnold R. Krakower Foundation. 38
PLATELET AS AN INFLAMMATORY CELL
1. 2. 3. 4. 5.
39
TABLE I Platelets as a Special Form of Leukocyte Lysosomal granule constituents Degranulation with release Accumulate in vessels adjacent to inflammation Interact with bacteria, viruses, antigen-antibody complexes Efferent arm-intravascular inflammation
uents which increase vascular permeability.2 In order to clarify the role of the platelet as a participant in the inflammatory response we have compared this cell to an orthodox mediator of inflammatory reactionsthe exudative polymorphonuclear leukocyte. Early inflammatory changes in damaged tissues involve the release of various biologically active materials from the lysosomes of polymorphonuclear leukocytes including a group of cationic proteins. This family of proteins mediates an entire spectrum of activities including antibacterial activity,3 increased vascular permeability,4 fever production,5 and anticoagulant activity.6 Cationic lysosomal proteins appear to be important contributors to the inflammatory process. We have examined platelets for these activities. ENHANCED VASCULAR PERMEABILITY EFFECTS Cationic proteins extracted from isolated human platelet granules lead to increased vascular permeability in rabbit skin. Human granule cationic protein was prepared by extracting isolated washed human platelet granules with dilute H2SO4. The acid extracts were cleared by centrifugation, neutralized, lyophilized and dialyzed against buffered saline (pH 7.4). Permeability-inducing activity was evaluated by injecting intradermally 0.1 ml of the sample into the skin of a rabbit which had previously received an intravenous injection of Evans blue dye. This agent binds to circulating albumin and leaks into tissues as a result of increased vascular permeability. Intradermal platelet extract led to dye extravasation into the rabbit skin. This increased vascular permeability induced by the platelet extract was completely inhibited when the intradermal challenge was made into an antihistamine-treated site. At two hours a secondary or delayed increase in vascular permeability was observed in the challenged intradermal site. It is of particular significance that no increase in vascular permeability was demonstrable using granule extract obtained from circulating human polymorphonuclear leukocytes. The biphasic permeability-enhancing effect was best observed in the rabbit skin when the response was compared in antihistamine- and non-antihistamine-treated rabbits at two different time intervals. Injection of the platelet extract into the skin of an Evans blue treated rabbit produced an acute permeability effect visible in 15 minutes. The secondary or delayed permeability effect was characterized by the slow progressive increase in permeability
40
NACHMAN AND POLLEY
at the intradermal challenge site, reaching a maximum in approximately 3 hours. The acute (15 minute) increase in permeability was blocked by prior injection of the antihistamine chlorpheniramine. Antihistamine did not block the delayed (180 minute) permeability effect. In order to define in clearer pharmacologic terms the nature of the permeability factor(s) in the platelet extract, various inhibition experiments were performed. Histamine and serotonin were not detected in the dialyzed extract by fluorimetric analysis. Incubation of the platelet protein extract with various inhibitor agents such as methysergide, soy bean trypsin inhibitor, carboxypeptidase B, and C1 inactivator did not significantly inhibit the acute or delayed permeability-enhancing effect. Thus the platelet granule extract did not contain serotonin, plasmin, bradykinin, PF/dil or kallikrein.7 Previous studies employing rabbit exudative polymorphonuclear leukocytes have shown that these cells contain small molecular weight permeability-enhancing proteins which cause histamine release from mast cells.8 Similar mastocytolytic activity was demonstrated using the human platelet granule extract.7 Histologic changes in the skin site 15 minutes after the platelet extract injection consisted of edema of the perivascular tissue with dilation of the capillaries and venules. In marked contrast, polymorphonuclear infiltration in the tissues was observed in the skin of an animal 3 hours after the platelet extract injection into an antihistamine-pretreated site. Partial chemical characterization of the human platelet permeability factor(s) was performed by DEAE and sephadex column chromatography.9 The biologic activity was localized to a cationic protein fraction of approximate 30,000 molecular weight. COMPLEMENT-PLATELET INTERACTIONS In addition to their leukocyte-like functions, it has become evident in recent years that platelets may also participate in inflammatory responses by interacting with the complement system. Thus platelet aggregation and release can be initiated by zymosan particles which have activated the alternative pathway of complement activation.10 Conversely human platelets upon aggregation release enzymes which directly activate the fifth component of complement-producing chemotactic activity for leukocytes.11 It is probable that the delayed permeability-enhancing effect of the platelet cationic granule factor is due to this C5 dependent neutrophilic chemotaxis. A clotting abnormality related to abnormal platelet function has been reported in rabbits congenitally deficient in C6. 12 13 C5b-9 complexes have been demonstrated on the human platelet membrane following the incubation of platelets in fresh human serum.'4 In addition, retraction and lysis of thrombin-induced blood clots was
41
PLATELET AS AN INFLAMMATORY CELL
inhibited by antiserum to C3 and C4.15 We have reported that complement-dependent ultrastructural lesions were visualized on the platelet surface subsequent to their incubation with thrombin and complement."6 To clarify these relationships we have studied the thrombin-mediated platelet specific uptake of purified radiolabeled complement components (Table II). Activation of complement on the platelet surface by either the classic (antibody) or the alternative (inulin) pathway led to uptake of 40-60,000 molecules of C3 per cell and 3-4,000 molecules of C5. Incubation of platelets with complement in the presence of thrombin led to a similar uptake of C5 but to a reduced uptake of C3. The specificity of the platelet in this reaction was demonstrated by the fact that no complement uptake was detected following incubation of thrombin with erythrocytes or leukocytes. While complement was not essential for thrombin-mediated platelet aggregation and release of serotonin, these two activities were significantly enhanced in the presence of complement. C3, C5, C6, C7, C8 and C9 were essential for this enhanced reactivity; however these six components in the absence of any previously described C3 convertase were the only components of the complement system that were required. These studies suggest a new pathway of complement activation-one that is dependent on the presence of thrombin and the platelet membrane and enters the known complement sequence at the C3 stage (Fig. 1). CONCLUSION The fact that human platelets contain an intracellular permeabilityenhancing protein system further strengthens the analogy of these cells to exudative polymorphonuclear leukocytes. One important difference should be stressed when comparing the platelet inflammatory system to TABLE II Platelet Complement Uptake Activation of complement* induced by:
Thrombin Inulin Antibody
Number of molecules per platelet C3
C5
4,400 61,600 39,800
3,600 2,900 4,200
FIG. 1. Complement activation mechanisms.
42
NACHMAN AND POLLEY
the leukocyte inflammatory system. To date, the leukocyte intracellular cationic protein mediators of inflammatory responses have been detected only in exudative cells. In contrast these same activities appear to reside preformed in circulating platelets. Thus the platelet possesses a precommitted exudative function. Whether this function represents a phylogenetic vestige of little physiologic importance or in fact is the basis of the platelet's role in mediating early blood vessel responses to focal inflammatory stimuli remains to be determined. The fact that thrombin and the platelet membrane appear to generate complement activation adds further ammunition to the platelet's inflammatory arsenal. It may be that activated complement components on the platelet surface also modulate the degree of cell participation in early hemostatic events. There is evidence which suggests that platelets do in fact participate in inflammatory responses. Thus platelets accumulate in blood vessels adjacent to areas of inflammation and tissue damage.'7 Human kidney transplant rejections may be associated with the formation of platelet aggregates in renal vessels. A similar phenomenon may characterize the kidney changes seen in the generalized Schwartzmann reaction. Various stimuli, including circulating antigen-antibody complexes, bacteria, and endotoxin, as well as endothelial disruption may lead to platelet aggregation, degranulation and release of cationic inflammatory mediators. Other released platelet constituents such as cathepsins, prostaglandin endoperoxides, thromboxane A2 and a connective tissue-activating peptide"8 also contribute to the propagation of the inflammatory response. Platelets also release a smooth muscle cell mitogenic factor which may play an important role in the development of atherosclerotic lesions.'9 The interesting pathogenetic possibility has been raised that platelet aggregates in flowing blood may initiate damage on a normal endothelial surface' leading to vascular lesions in the microcirculation. It is probable that release of cationic permeability proteins from aggregated platelets as well as complement activation on the platelet surface may contribute to these early vascular abnormalities. 1.
2. 3.
4.
REFERENCES MARCUS, A. J., ZUCKER-FRANKLIN, D., SAFIER, L. B., AND ULLMAN, H.: Studies on human platelet granules and membranes. J. Clin. Invest. 45: 14, 1966. PACKHAM, M. A., NISHIZAWA, E. E., AND MUSTARD, J. F.: Response of platelets to tissue injury. Biochem. Pharmacol. (Suppl.) 17: 171, 1968. SPITZNAGEL, J. K., AND ZEYA, H. I.: Basic proteins and leukocyte lysosomes as biochemical determinants of resistance to infection. Trans. Assoc. Amer. Physicians. 77: 126, 1964. SEEGER, W., AND JANOFF, A.: Mediators of inflammation in leukocyte lysosomes. VI. Partial purification and characterization of a mast cell rupturing component. J. Exp. Med. 124: 833, 1966.
PLATELET AS AN INFLAMMATORY CELL
43
5. HERION, J. C., SPITZNAGEL, J. K., WALKER, R. I., AND ZEYA, H. I.: Pyrogenicity of granulocyte lysosomes. Amer. J. Physiol. 211: 693, 1966. 6. SABA, H. I., ROBERTS, H. R., AND HERION, J. C.: The anticoagulant activity of lysosomal cationic proteins from polymorphonuclear leukocytes. J. Clin. Invest. 46: 580, 1967. 7. NACHMAN, R., WEKSLER, B., AND FERRIS, B.: Increased vascular permeability produced by human platelet granule cationic extract. J. Clin. Invest. 49: 274, 1970. 8. RANADIVE, N. S., AND COCHRANE, C. G.: Isolation and characterization of permeability factors from rabbit neutrophiles. J. Exp. Med. 128: 605, 1968. 9. NACHMAN, R., WEKSLER, B., AND FERRIS, B.: Characterization of human platelet vascular permeability enhancing activity. J. Clin. Invest. 51: 549, 1972. 10. ZUCKER, M. B., AND GRANT, R. A.: Aggregation and release reaction induced in human blood platelets by zymosan. J. Immunol. 112: 1219, 1974. 11. WEKSLER, B., AND COUPAL, C. E.: Platelet dependent generation of chemotactic activity in serum. J. Exp. Med. 137: 1419, 1973. 12. ZIMMERMAN, T. S., ANOGRAVE, C. M., AND MULLER-EBERHARD, H. J.: A blood coagulation abnormality in rabbits deficient in the sixth component of complement (C6) and its correction by purified C6. J. Exp. Med. 134: 1591, 1971. 13. ZIMMERMAN, T. S., AND MtOLLER-EBERHARD, H. F.: Blood coagulation initiation by a complement-mediated pathway. J. Exp. Med. 134: 1601, 1971. 14. ZIMMERMAN, T. S., AND KOLB, W. P.: Human platelet-initiated formation and uptake of the C5-9 complex of human complement. J. Clin. Invest. 57: 203, 1976. 15. TAYLOR, F. B., AND MULLER-EBERHARD, H. F.: Qualitative description of factors involved in the retraction and lysis of dilute whole blood clots and in the aggregation and retraction of platelets. J. Clin. Invest. 49: 2068, 1970. 16. POLLEY, M. J., AND NACHMAN, R. L.: Ultrastructural lesions on the surface of platelets associated with either blood coagulation or with antibody-mediated immune injury. J. Exp. Med. 141: 1261, 1975. 17. COTRAN, R. S.: The delayed and prolonged vascular leakage in inflammation. II. An electron microscopic study of the vascular response after thermal injury. Amer. J. Path. 46: 589, 1965. 18. CASTOR, C. W., RITCHIE, J. C., SCOTT, M. E., AND WHITNEY, S. L.: Connective tissue activation XI. Stimulation of glycosaminoglycan and DNA formation by a platelet factor. Arthritis Rheum. 20: 859, 1977. 19. RoSS, R., GLOMSET, J., KARIYA, B., AND HARKER, L.: A platelet dependent serum factor that stimulates the proliferation of arterial smooth muscle cells in vitro. Proc. Natl. Acad. Sci. U.S.A. 71: 1207, 1974. 20. JORGENSON, L., HOVIG, T., KORSELL, H. C., AND MUSTARD, J. F.: Adenosine diphosphate induced platelet aggregation and vascular injury in swine and rabbits. Amer. J. Path. 61: 161, 1970.
One of the earliest steps in the primary hemostatic defense mechanism involves the adhesion of circulating platelets to denuded subendothelial structures such as collagen, basement membrane, and microfibrils in the vicinity of a damaged endothelial surface. Collagen-activated platelets induce the release of intracellular constituents including ADP, serotonin and products of the arachidonate transformation pathway. The released ADP, thromboxane A2 and prostaglandin endoperoxides formed from arachidonate lead to the formation of a platelet aggregate which eventually plugs and seals off the disrupted vessel. It is now generally considered that this sequence of events contributes to the genesis and development of the white thrombus in human pathology and may play a signal role in the atherogenesis. This primary hemostatic response involving the platelet blood vessel wall reaction in mammals resembles to a significant extent the basic cellular defense mechanisms of more primitive forms such as invertebrates. Human platelets contain intracellular granules similar to the classical lysosomes of polymorphonuclear leukocytes' and contribute to the inflammatory response accompanying tissue injury by releasing constituents which may alter blood vessel reactivity. Platelets accumulate in vessels adjacent to inflammatory sites and interact with bacteria, viruses, and antigen-antibody complexes. Platelets and polymorphonuclear leukocytes have the same primitive phylogenetic ancestor and perform similar inflammatory functions although in different geographic settings. The platelet performs its functions in the intravascular compartment while the polymorphonuclear leukocyte performs its major functions in extravascular spaces. The primary hemostatic response involving the platelet blood vessel wall reaction in higher forms such as mammals appears to have retained a phylogenetic vestige of primitive leukocyte behavior. In this regard, it is useful to consider primary hemostasis as basically an inflammatory response and thus the platelet can be thought of as a special form of leukocyte (Table I). Several years ago it was demonstrated that platelets contribute to the inflammatory response accompanying tissue injury by releasing constitDepartment of Medicine, Cornell University Medical College, New York City. Supported by NIH grant (HL18828) and the Arnold R. Krakower Foundation. 38
PLATELET AS AN INFLAMMATORY CELL
1. 2. 3. 4. 5.
39
TABLE I Platelets as a Special Form of Leukocyte Lysosomal granule constituents Degranulation with release Accumulate in vessels adjacent to inflammation Interact with bacteria, viruses, antigen-antibody complexes Efferent arm-intravascular inflammation
uents which increase vascular permeability.2 In order to clarify the role of the platelet as a participant in the inflammatory response we have compared this cell to an orthodox mediator of inflammatory reactionsthe exudative polymorphonuclear leukocyte. Early inflammatory changes in damaged tissues involve the release of various biologically active materials from the lysosomes of polymorphonuclear leukocytes including a group of cationic proteins. This family of proteins mediates an entire spectrum of activities including antibacterial activity,3 increased vascular permeability,4 fever production,5 and anticoagulant activity.6 Cationic lysosomal proteins appear to be important contributors to the inflammatory process. We have examined platelets for these activities. ENHANCED VASCULAR PERMEABILITY EFFECTS Cationic proteins extracted from isolated human platelet granules lead to increased vascular permeability in rabbit skin. Human granule cationic protein was prepared by extracting isolated washed human platelet granules with dilute H2SO4. The acid extracts were cleared by centrifugation, neutralized, lyophilized and dialyzed against buffered saline (pH 7.4). Permeability-inducing activity was evaluated by injecting intradermally 0.1 ml of the sample into the skin of a rabbit which had previously received an intravenous injection of Evans blue dye. This agent binds to circulating albumin and leaks into tissues as a result of increased vascular permeability. Intradermal platelet extract led to dye extravasation into the rabbit skin. This increased vascular permeability induced by the platelet extract was completely inhibited when the intradermal challenge was made into an antihistamine-treated site. At two hours a secondary or delayed increase in vascular permeability was observed in the challenged intradermal site. It is of particular significance that no increase in vascular permeability was demonstrable using granule extract obtained from circulating human polymorphonuclear leukocytes. The biphasic permeability-enhancing effect was best observed in the rabbit skin when the response was compared in antihistamine- and non-antihistamine-treated rabbits at two different time intervals. Injection of the platelet extract into the skin of an Evans blue treated rabbit produced an acute permeability effect visible in 15 minutes. The secondary or delayed permeability effect was characterized by the slow progressive increase in permeability
40
NACHMAN AND POLLEY
at the intradermal challenge site, reaching a maximum in approximately 3 hours. The acute (15 minute) increase in permeability was blocked by prior injection of the antihistamine chlorpheniramine. Antihistamine did not block the delayed (180 minute) permeability effect. In order to define in clearer pharmacologic terms the nature of the permeability factor(s) in the platelet extract, various inhibition experiments were performed. Histamine and serotonin were not detected in the dialyzed extract by fluorimetric analysis. Incubation of the platelet protein extract with various inhibitor agents such as methysergide, soy bean trypsin inhibitor, carboxypeptidase B, and C1 inactivator did not significantly inhibit the acute or delayed permeability-enhancing effect. Thus the platelet granule extract did not contain serotonin, plasmin, bradykinin, PF/dil or kallikrein.7 Previous studies employing rabbit exudative polymorphonuclear leukocytes have shown that these cells contain small molecular weight permeability-enhancing proteins which cause histamine release from mast cells.8 Similar mastocytolytic activity was demonstrated using the human platelet granule extract.7 Histologic changes in the skin site 15 minutes after the platelet extract injection consisted of edema of the perivascular tissue with dilation of the capillaries and venules. In marked contrast, polymorphonuclear infiltration in the tissues was observed in the skin of an animal 3 hours after the platelet extract injection into an antihistamine-pretreated site. Partial chemical characterization of the human platelet permeability factor(s) was performed by DEAE and sephadex column chromatography.9 The biologic activity was localized to a cationic protein fraction of approximate 30,000 molecular weight. COMPLEMENT-PLATELET INTERACTIONS In addition to their leukocyte-like functions, it has become evident in recent years that platelets may also participate in inflammatory responses by interacting with the complement system. Thus platelet aggregation and release can be initiated by zymosan particles which have activated the alternative pathway of complement activation.10 Conversely human platelets upon aggregation release enzymes which directly activate the fifth component of complement-producing chemotactic activity for leukocytes.11 It is probable that the delayed permeability-enhancing effect of the platelet cationic granule factor is due to this C5 dependent neutrophilic chemotaxis. A clotting abnormality related to abnormal platelet function has been reported in rabbits congenitally deficient in C6. 12 13 C5b-9 complexes have been demonstrated on the human platelet membrane following the incubation of platelets in fresh human serum.'4 In addition, retraction and lysis of thrombin-induced blood clots was
41
PLATELET AS AN INFLAMMATORY CELL
inhibited by antiserum to C3 and C4.15 We have reported that complement-dependent ultrastructural lesions were visualized on the platelet surface subsequent to their incubation with thrombin and complement."6 To clarify these relationships we have studied the thrombin-mediated platelet specific uptake of purified radiolabeled complement components (Table II). Activation of complement on the platelet surface by either the classic (antibody) or the alternative (inulin) pathway led to uptake of 40-60,000 molecules of C3 per cell and 3-4,000 molecules of C5. Incubation of platelets with complement in the presence of thrombin led to a similar uptake of C5 but to a reduced uptake of C3. The specificity of the platelet in this reaction was demonstrated by the fact that no complement uptake was detected following incubation of thrombin with erythrocytes or leukocytes. While complement was not essential for thrombin-mediated platelet aggregation and release of serotonin, these two activities were significantly enhanced in the presence of complement. C3, C5, C6, C7, C8 and C9 were essential for this enhanced reactivity; however these six components in the absence of any previously described C3 convertase were the only components of the complement system that were required. These studies suggest a new pathway of complement activation-one that is dependent on the presence of thrombin and the platelet membrane and enters the known complement sequence at the C3 stage (Fig. 1). CONCLUSION The fact that human platelets contain an intracellular permeabilityenhancing protein system further strengthens the analogy of these cells to exudative polymorphonuclear leukocytes. One important difference should be stressed when comparing the platelet inflammatory system to TABLE II Platelet Complement Uptake Activation of complement* induced by:
Thrombin Inulin Antibody
Number of molecules per platelet C3
C5
4,400 61,600 39,800
3,600 2,900 4,200
FIG. 1. Complement activation mechanisms.
42
NACHMAN AND POLLEY
the leukocyte inflammatory system. To date, the leukocyte intracellular cationic protein mediators of inflammatory responses have been detected only in exudative cells. In contrast these same activities appear to reside preformed in circulating platelets. Thus the platelet possesses a precommitted exudative function. Whether this function represents a phylogenetic vestige of little physiologic importance or in fact is the basis of the platelet's role in mediating early blood vessel responses to focal inflammatory stimuli remains to be determined. The fact that thrombin and the platelet membrane appear to generate complement activation adds further ammunition to the platelet's inflammatory arsenal. It may be that activated complement components on the platelet surface also modulate the degree of cell participation in early hemostatic events. There is evidence which suggests that platelets do in fact participate in inflammatory responses. Thus platelets accumulate in blood vessels adjacent to areas of inflammation and tissue damage.'7 Human kidney transplant rejections may be associated with the formation of platelet aggregates in renal vessels. A similar phenomenon may characterize the kidney changes seen in the generalized Schwartzmann reaction. Various stimuli, including circulating antigen-antibody complexes, bacteria, and endotoxin, as well as endothelial disruption may lead to platelet aggregation, degranulation and release of cationic inflammatory mediators. Other released platelet constituents such as cathepsins, prostaglandin endoperoxides, thromboxane A2 and a connective tissue-activating peptide"8 also contribute to the propagation of the inflammatory response. Platelets also release a smooth muscle cell mitogenic factor which may play an important role in the development of atherosclerotic lesions.'9 The interesting pathogenetic possibility has been raised that platelet aggregates in flowing blood may initiate damage on a normal endothelial surface' leading to vascular lesions in the microcirculation. It is probable that release of cationic permeability proteins from aggregated platelets as well as complement activation on the platelet surface may contribute to these early vascular abnormalities. 1.
2. 3.
4.
REFERENCES MARCUS, A. J., ZUCKER-FRANKLIN, D., SAFIER, L. B., AND ULLMAN, H.: Studies on human platelet granules and membranes. J. Clin. Invest. 45: 14, 1966. PACKHAM, M. A., NISHIZAWA, E. E., AND MUSTARD, J. F.: Response of platelets to tissue injury. Biochem. Pharmacol. (Suppl.) 17: 171, 1968. SPITZNAGEL, J. K., AND ZEYA, H. I.: Basic proteins and leukocyte lysosomes as biochemical determinants of resistance to infection. Trans. Assoc. Amer. Physicians. 77: 126, 1964. SEEGER, W., AND JANOFF, A.: Mediators of inflammation in leukocyte lysosomes. VI. Partial purification and characterization of a mast cell rupturing component. J. Exp. Med. 124: 833, 1966.
PLATELET AS AN INFLAMMATORY CELL
43
5. HERION, J. C., SPITZNAGEL, J. K., WALKER, R. I., AND ZEYA, H. I.: Pyrogenicity of granulocyte lysosomes. Amer. J. Physiol. 211: 693, 1966. 6. SABA, H. I., ROBERTS, H. R., AND HERION, J. C.: The anticoagulant activity of lysosomal cationic proteins from polymorphonuclear leukocytes. J. Clin. Invest. 46: 580, 1967. 7. NACHMAN, R., WEKSLER, B., AND FERRIS, B.: Increased vascular permeability produced by human platelet granule cationic extract. J. Clin. Invest. 49: 274, 1970. 8. RANADIVE, N. S., AND COCHRANE, C. G.: Isolation and characterization of permeability factors from rabbit neutrophiles. J. Exp. Med. 128: 605, 1968. 9. NACHMAN, R., WEKSLER, B., AND FERRIS, B.: Characterization of human platelet vascular permeability enhancing activity. J. Clin. Invest. 51: 549, 1972. 10. ZUCKER, M. B., AND GRANT, R. A.: Aggregation and release reaction induced in human blood platelets by zymosan. J. Immunol. 112: 1219, 1974. 11. WEKSLER, B., AND COUPAL, C. E.: Platelet dependent generation of chemotactic activity in serum. J. Exp. Med. 137: 1419, 1973. 12. ZIMMERMAN, T. S., ANOGRAVE, C. M., AND MULLER-EBERHARD, H. J.: A blood coagulation abnormality in rabbits deficient in the sixth component of complement (C6) and its correction by purified C6. J. Exp. Med. 134: 1591, 1971. 13. ZIMMERMAN, T. S., AND MtOLLER-EBERHARD, H. F.: Blood coagulation initiation by a complement-mediated pathway. J. Exp. Med. 134: 1601, 1971. 14. ZIMMERMAN, T. S., AND KOLB, W. P.: Human platelet-initiated formation and uptake of the C5-9 complex of human complement. J. Clin. Invest. 57: 203, 1976. 15. TAYLOR, F. B., AND MULLER-EBERHARD, H. F.: Qualitative description of factors involved in the retraction and lysis of dilute whole blood clots and in the aggregation and retraction of platelets. J. Clin. Invest. 49: 2068, 1970. 16. POLLEY, M. J., AND NACHMAN, R. L.: Ultrastructural lesions on the surface of platelets associated with either blood coagulation or with antibody-mediated immune injury. J. Exp. Med. 141: 1261, 1975. 17. COTRAN, R. S.: The delayed and prolonged vascular leakage in inflammation. II. An electron microscopic study of the vascular response after thermal injury. Amer. J. Path. 46: 589, 1965. 18. CASTOR, C. W., RITCHIE, J. C., SCOTT, M. E., AND WHITNEY, S. L.: Connective tissue activation XI. Stimulation of glycosaminoglycan and DNA formation by a platelet factor. Arthritis Rheum. 20: 859, 1977. 19. RoSS, R., GLOMSET, J., KARIYA, B., AND HARKER, L.: A platelet dependent serum factor that stimulates the proliferation of arterial smooth muscle cells in vitro. Proc. Natl. Acad. Sci. U.S.A. 71: 1207, 1974. 20. JORGENSON, L., HOVIG, T., KORSELL, H. C., AND MUSTARD, J. F.: Adenosine diphosphate induced platelet aggregation and vascular injury in swine and rabbits. Amer. J. Path. 61: 161, 1970.
