ovalbumin and Thrombocytopenia

There is considerable evidence that platelet activation occurs in allergic airways diseases. In this study we aimed to investigate platelet adhesion to immobilized fibrinogen and intracellular calcium levels in a rat model of allergic inflammation. Male Wistar rats were challenged with ovalbumin (OVA). At 30 min to 24h after OVA-challenge, assays of platelet adhesion to immobilized fibrinogen and intracellular calcium levels using fura 2-AM loaded platelets were performed. The serum levels of IgE were approximately 5-fold greater in OVA-sensitized rats. A marked eosinophil influx in bronchoalveolar lavage (BAL) fluid of OVA-challenged rats at 24h after OVA-challenge was also seen. OVA-challenge resulted in a marked thrombocytopenia, as observed within 12h after OVA-challenge. The agonists ADP (0.5-50 microM) and thrombin (30-100 mU/ml) concentration-dependently increased platelet adhesion to immobilized fibrinogen. At an early time after OVA-challenge (30 min), platelets exhibited greater platelet adhesion compared with the non-sensitized group, whereas at a late time (24h) they exhibited lower platelet adhesion to both agonists. Moreover, at 30 min after OVA-challenge, intracellular calcium levels to ADP (20 microM) and thrombin (100 mU/ml)-activated platelets were greater compared with non-challenged rats. As opposed, at 24h after OVA challenge, a lower intracellular calcium level to ADP- and thrombin-activated platelets was observed. In conclusion, OVA-challenge in rats promotes a biphasic response in platelet adhesion consisting of an increased adhesion and intracellular calcium levels at an early phase (30 min), which progress to a reduction in adhesion and intracellular calcium levels at a late time (24h) after antigen challenge.

Topics: Adenosine Diphosphate; Animals; Bronchoalveolar Lavage Fluid; Calcium; Disease Models, Animal; Dose-Response Relationship, Drug; Fibrinogen; Immunoglobulin E; Inflammation; Lung; Male; Ovalbumin; Platelet Adhesiveness; Rats; Rats, Wistar; Thrombin; Thrombocytopenia; Time Factors

Asthma is associated with airway remodeling. Evidence of platelet recruitment to the lungs of asthmatics after allergen exposure suggests platelets participate in various aspects of asthma; although their importance is unknown in the context of airway remodeling, their involvement in atherosclerosis is established. Studies from our laboratory have shown a requirement for platelets in pulmonary leukocyte recruitment in a murine model of allergic lung inflammation. Presently, the effects of platelet depletion and corticosteroid administration on airway remodeling and lung function were examined. Ovalbumin (OVA)-sensitized mice, exposed to aerosolized OVA for 8 weeks, demonstrated epithelial and smooth muscle thickening, and subepithelial reticular fiber deposition in the distal airways. The depletion of platelets via an immunologic (antiplatelet antisera) or nonimmunologic (busulfan) method, markedly reduced airway remodeling. In contrast, dexamethasone administration did not affect epithelial thickening or subepithelial fibrosis, despite significantly inhibiting leukocyte recruitment. Thus, pathways leading to certain aspects of airway remodeling may not depend on leukocyte recruitment, whereas platelet activation is obligatory. OVA-sensitized mice exhibited airway hyperresponsiveness (AHR) compared with sham-sensitized mice following chronic OVA exposure. Neither platelet depletion nor dexamethasone administration inhibited chronic AHR; thus, mechanisms other than inflammation and airway remodeling may be involved in the pathogenesis of chronic AHR.

Topics: Adrenal Cortex Hormones; Animals; Asthma; Blood Platelets; Bronchoalveolar Lavage Fluid; Dexamethasone; Disease Models, Animal; Hypersensitivity; Immunoglobulin E; Inflammation; Leukocytes; Mice; Mice, Inbred C57BL; Ovalbumin; Platelet Count; Pulmonary Circulation; Respiratory Function Tests; Respiratory Mucosa; Thrombocytopenia

The allelic human platelet alloantigens PIA1/PIA2 are determined by a 33 Leu-Pro substitution in the second disulfide loop of the integrin beta3 subunit of the fibrinogen receptor, alphaIIb beta3 (GPIIb-IIIa). Alloantibodies to PIA1 cause neonatal alloimmune thrombocytopenia. We studied the suppression of specific Ab production to a disulfide-looped peptide spanning the polymorphic region of integrin beta3, 24AWCSDEALPLGSPRCD39 (LPL). Mice immunized with LPL coupled to OVA (LPL-OVA) produced Abs specific for LPL. When immunized animals were injected with low m.w. dextran heavily derivitized with LPL (Dex(low)LPL(high)), levels of Ab to LPL fell immediately and remained low 1 mo later. Both high affinity and total Abs were affected. Arrays with lower peptide density or a high m.w. backbone did not induce well sustained suppression. Abs to OVA were unaffected by the arrays. Naive mice given Dex(low)LPL(high) were tolerant to subsequent immunization with LPL-OVA. In transfer experiments, irradiated recipients of spleen cells or purified 8 cells from animals suppressed with Dex(low)LPL(high) did not respond to LPL-OVA. Spleen cells from suppressed animals did not suppress the response to LPL-OVA in recipients of immune B cells. These results demonstrate that peptide arrays, by a mechanism sensitive to molecular configuration, induce tolerance to peptide immunization and suppress an ongoing, high affinity Ab response. Peptide arrays induce the elimination or irreversible anergy of specific memory B cells and do not require a non-B spleen cell population to maintain suppression.

Topics: Amino Acid Sequence; Animals; Antigens, CD; Chickens; Female; Humans; Immune Tolerance; Immunization; Immunoglobulin G; Infant, Newborn; Integrin beta3; Integrins; Isoantibodies; Isoantigens; Mice; Mice, Inbred BALB C; Molecular Sequence Data; Molecular Weight; Ovalbumin; Peptides; Platelet Membrane Glycoproteins; Thrombocytopenia

The antagonism by prostacyclin (PG12) and prostaglandin E1 (PGE1) of bronchoconstriction induced by serotonin (5HT), collagen, arachidonic acid (AA) and anaphylaxis, as well as of thrombocytopenia was studied in the guinea-pig. Under conditions where PGE1 prevented bronchoconstriction by 5HT, by collagen or by AA better than the accompanying thrombocytopenia, PG12 was a selective antagonist of bronchoconstriction due to collagen, but failed to interfere with that due to 5HT or to AA. Collagen-induced bronchoconstriction in the guinea-pig is platelet-dependent. PG12 blocks bronchoconstriction by collagen, because it prevents the platelet activation, and fails to interfere with bronchoconstriction by AA, even though it reduces the accompanying thrombocytopenia, because the role of platelets is negligible. PGE1 and PG12 failed to interfere with thrombocytopenia or with bronchoconstriction of anaphylactic shock, and were inactive even when the acute bronchial effect was suppressed by anti-histamine treatment. Anaphylactic thrombocytopenia is beyond the control of agents which stimulate the cyclic AMP system, and involves specific mechanism which are not stimulated in platelet-rich plasma.

Topics: Anaphylaxis; Animals; Arachidonic Acids; Blood Platelets; Bronchi; Collagen; Epoprostenol; Guinea Pigs; Muscle Contraction; Muscle, Smooth; Ovalbumin; Platelet Aggregation; Prostaglandins; Prostaglandins E; Serotonin Antagonists; Thrombocytopenia

The anti-inflammatory activity of aspirin-like drugs could derive, at least in part, by inhibiting synthesis and release of prostaglandins or rabbit aorta-contracting substance from platelets. Indeed, aggregation of platelets and the consequent release of inflammatory mediators has been frequently evoked as a factor in the development of the inflammatory reaction. The participation of platelets in acute inflammation was tested in three types of trauma in rats rendered thrombocytopenic with anti-platelet serum. Oedema in response to carrageenin, anti-platelet serum or passive cutaneous anaphylaxis was no different from the controls in thrombocytopenic rats.

Topics: Acute Disease; Animals; Blood Platelets; Carrageenan; Edema; Immune Sera; Inflammation; Ovalbumin; Passive Cutaneous Anaphylaxis; Rats; Thrombocytopenia

Topics: Acute Disease; Anaphylaxis; Animals; Apnea; Carotid Arteries; Erythrocyte Count; Hemodynamics; Histamine; Hypersensitivity, Immediate; Hypertension; Hypertension, Pulmonary; Leukocyte Count; Leukopenia; Ovalbumin; Swine; Swine Diseases; Thrombocytopenia

Topics: Animals; Antigen-Antibody Complex; Blood Cell Count; Blood Platelets; Disseminated Intravascular Coagulation; Factor V; Female; Fibrin; Fibrinogen; Immunization; Immunoglobulin G; Male; Ovalbumin; Rabbits; Thrombocytopenia

Topics: Animals; Antigens; Blood Cell Count; Blood Platelets; Blood Pressure; Enzyme Activation; Fibrin; Fibrinogen; Fibrinolysis; Immunoelectrophoresis; Ovalbumin; Plasma; Rabbits; Streptokinase; Thrombocytopenia; Time Factors