Significant Reduction in the Binding of a Monoclonal Antibody (LYP 18) Directed Against the IIb/IIIa Glycoprotein Complex to Platelets of Patients Having Undergone Extracorporeal Circulation

Physiopathology and Management of Coagulation during Long-term Extracorporeal Respiratory Assistance

Thrombohemorrhagic risk is one of the main limiting factors in extracorporeal circulation. We describe here our experience in managing some life-threatening hematological complications in 58 patients with acute respiratory failure treated with long-term extracorporeal assistance. These patients were studied by clinical and laboratory means to assess questions related to heparin monitoring, coagulation complications and bleeding incidence. We found that two clotting tests, activated partial thromboplastin time (APTT) and activated clotting time (ACT) can be easily used to assess the safety of anticoagulant treatment (therapeutic ranges: APTT from 55 to 95 sec and ACT from 170 to 220 sec). A certain degree of coagulation activation, despite heparin, was indicated by the constant finding of thrombin-antithrombin complexes, while fibrinolytic activation, measured as plasminogen activator activity, was confined to the time of bypass connection and was of no clinical consequence. Platelet function was always impaired without relation to the platelet loss. Disseminated intravascular coagulation (DIC) (13 episodes) and severe bleeding (11 episodes) were major complications. DIC was corrected with a good outcome for 8 of 13 patients, while severe bleeding was correlated with a poor outcome in 8 of the 11 patients, probably because of the severity of the underlying disease.

Platelet analysis using flowcytometric procedures

'Ex vivo' testing of functional platelet properties using conventional techniques reflects the overall behaviour of the whole platelet population in the sample under investigation. Since many functional aspects depend on ultrastructural constituents which may vary from one cell to another, multiparameter single cell analysis of platelets may be advantageous in providing direct insight into deviations at the cellular level relevant to the pathophysiology of disease states such as bleeding disorders or thrombophilia. Immunolabelling with monoclonal antibodies against membrane antigens has been combined with flowcytometry to provide a standardized, highly specific and sensitive analytical tool. The assay has been optimized for simultaneous two colour fluorescence staining, and this allows the testing of whole blood to provide a quick monitoring method for the differential diagnosis of thrombasthenic diseases like Bernard Soulier's syndrome or Glanzmann's thrombasthenia in which typical staining patterns lack the specific fluorescence for glycoproteins Ib and IIb/IIIa respectively. Also changes in the antigenicity of the outer membrane of activated platelets are detectable with monoclonal antibodies against specific antigenic epitopes such as thrombospondin (a secretion marker) or α-granule and lysosomal proteins (extrusion markers). However, for detection of activated platelets in diseases associated with a prethrombotic state, the procedures for immunolabelling platelets with monoclonal antibodies and instrumental detection sensitivity remain to be optimized. After further development, flowcytometric assays of the functional status of individual platelets may be superior to the measurement of the indirect plasma markers such as platelet factor 4 or β-thromboglobulin for routine diagnosis of the prethrombotic state.

Bleeding in Cardiac Surgery: Its Prevention and Treatment—an Evidence-Based Review

Expected and unexpected bleeding occur frequently in patients undergoing cardiac surgery. Bleeding after cardiac surgery can be broadly divided into two groups: surgical (unrecognized bleeding vessel, anastomosis, or other suture line) or nonsurgical bleeding (caused by coagulopathy). Factors influencing both surgical and nonsurgical bleeding can be further broken down into those occurring preoperatively and those that occur intraoperatively and postoperatively. A thorough understanding of these factors is necessary to reduce bleeding. This is a desirable clinical goal, because excessive bleeding is associated with adverse outcomes.

Platelet and leukocyte activation and design consequences for thoracic artificial lungs

Blood contact with the prosthetic surfaces of artificial lungs causes extensive activation of molecular and cellular mediators of coagulation and inflammation that can lead to patient morbidity and mortality. To determine the effects of artificial lung fiber bundle shear stress and surface area on blood activation, porcine blood was recirculated for 4 hours through circuits containing mock artificial lungs with bundle shear stresses of 11.6, 7.3, and 3.9 dynes/cm2 and surface areas of 5.2, 3.5, and 1.7 cm2/ml of circuit volume. Blood from these circuits was assayed for platelet and leukocyte counts, soluble P-selectin concentrations, and lactoferrin concentrations to determine the level of platelet and leukocyte adherence to the circuit, platelet activation, and leukocyte activation, respectively. Neither platelet nor leukocyte counts were significantly affected by shear stress or surface area. P-selectin and lactoferrin concentrations were significantly greater at a fiber bundle shear stress of 11.6 dynes/ cm2. P-selectin and lactoferrin concentrations were significantly greater at a fiber bundle surface area of 5.2 cm2/ml of circuit volume. Artificial lungs, therefore, should be designed with average bundle shear stresses < 11.6 dynes/cm2 and with surface areas < 5.2 cm2/ml of circuit volume. Current thoracic artificial lungs meet both these requirements.

SMA circuits reduce platelet consumption and platelet factor release during cardiac surgery

BACKGROUND

Platelet count and function are particularly damaged by cardiopulmonary bypass (CPB). This study evaluated the effects of a novel CPB circuit in terms of platelet count and activation, and postoperative need for blood products.

METHODS

One hundred patients undergoing coronary grafting were randomized in two groups: control group (n = 50) and test group (n = 50, surface modifying additives circuit, SMA group). Blood samples were taken before, during, and after CPB. Postoperative blood loss, number of transfused blood products, and postoperative variables were recorded.

RESULTS

The platelet count decreased less in the SMA group compared to the control group (end of CPB: respectively, 165 +/- 9 x 10(3)/mm3 vs 137 +/- 8 x 10(3)/mm3; p < 0.01). This was paralleled by a reduction in beta-thromboglobulin plasma levels in the SMA group. There was a trend to decreased blood loss in the SMA group, but the difference was significant only in patients taking aspirin preoperatively (p < 0.05). In the SMA group nearly 50% less fresh frozen plasma and platelet units were administered (p < 0.01). No operative deaths were observed.

CONCLUSIONS

The use of circuits with surface additives is clinically safe, preserves platelet levels, and attenuates platelet activation. This may lead to a reduced need for blood products.

Effects of extracorporeal circulation and heparin on the phenotype of platelet surface antigens following heart surgery

In this prospective study, the time-dependent effects of extracorporeal circulation and heparin-mediated effects on platelet surface antigens in vitro were investigated using whole blood flow cytometry. Blood samples were drawn prior to and following extracorporeal circulation in 89 patients. The response of surface antigen expression (glycoprotein IIb/IIIa, P-selectin, and glycoprotein Ib) with and without in vitro stimulation was measured. A significant correlation of the duration of extracorporeal circulation with the postoperative response of glycoprotein IIb/IIIa, glycoprotein Ib, and P-selectin to in vitro activation was found. Postoperative P-selectin and glycoprotein Ib expression stimulated with ADP correlated to blood loss. Heparin in vitro significantly reduced glycoprotein Ib expression. Heparin, as well as the duration of extracorporeal circulation, independently correlated to phenotypic changes of platelets following extracorporeal circulation. The significant correlation of these variables to postoperative blood loss demonstrates their relevance to platelet function in vivo.

Platelet protective effect of TAK-029, a novel glycoprotein IIb/IIIa antagonist: an in vitro study

Previous studies have indicated that exposure of fibrinogen receptors associated with the glycoprotein IIb/IIIa complex contributes to platelet loss during cardiopulmonary bypass. TAK-029 is a newly developed reversible, nonpeptide inhibitor of platelet glycoprotein IIb/IIIa receptors. In this study, we tested the platelet preserving effect of TAK-029 in an in vitro model. The methods included the comparison of the release of beta-thromboglobulin (beta-TG) between a TAK-029 group (n = 5) and a control group (n = 5) in a mock circulation under a shear force generated by a centrifugal pump. To evaluate the degree of beta-TG release, deltabeta-TG/deltaT was calculated where deltabeta-TG is the increase in beta-TG and deltaT is the time. The results showed that the value of deltabeta-TG/deltaT in the TAK-029 group was significantly lower than it was in the control group (4.22 +/- 0.27 x 10(2) ng/ml vs. 7.33 +/- 0.66 x 10(2) ng/ml, respectively). In conclusion, TAK-029 reduced the platelet activation under the shear forces of an in vitro model, suggesting that TAK-029 is a potential candidate for platelet protection during cardiopulmonary bypass.

Aprotinin Fifteen Years Later

Aprotinin, the broad-based bovine serine protease inhibitor, was first used as an antidote against the harmful proteases released through complement-induced neutrophil activation in the early 1980s. Since then, the safety and efficacy of aprotinin have been debated. Even now, fifteen years later, aprotinin's precise mechanism of action and clear indications for use have not been defined. This article discusses what aprotinin is, its role in the contact system of blood, how it improves hemostasis, the effect of temperature on it, its use in clinical practice, and which patients should receive it. The article concludes that aprotinin's hemostatic effects are useful in patients who are at increased risk from bleeding, but that it should not be considered a substitute for surgical skill. Early claims of absolute safety were premature. Risks between high- and low-dose regimens vary significantly, and more study is required. Alternatives to aprotinin such as the less expensive antifibrinolytic agent tranexamic acid are now available, but they also require additional study.

Monitoring of hemostasis in cardiac surgical patients: impact of point-of-care testing on blood loss and transfusion outcomes

Patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) are at increased risk for excessive perioperative blood loss requiring transfusion of blood products. Strategies to optimize administration of heparin and protamine and the assessment of their effects on coagulation are evolving in cardiac surgical patients. Two recent evaluations have focused on the use of multiple point-of-care (POC) coagulation assays for patient-specific adjustment of heparin and protamine dosage. These studies indicate that blood loss and transfusion requirements in cardiac surgical patients may be reduced with more accurate control of heparin anticoagulation and its reversal. Blood component administration in patients with excessive post-CPB bleeding is generally empiric in part, related to turnaround times of laboratory-based tests. Methods are now available for rapid, POC assessment of coagulation to allow appropriate, targeted therapy for acquired hemostatic abnormalities. Recent studies indicate that a rapid evaluation of thrombocytopenia and coagulation factor deficiencies with POC tests can facilitate the optimal administration of pharmacologic and transfusion-based therapy in patients who exhibit excessive bleeding after CPB. POC tests that assess platelet function have been developed, and their use may facilitate identification of which patients at risk for excessive blood loss may respond to pharmacologic interventions such as desmopressin acetate or antifibrinolytic agents.

Megakaryocytes and platelets in alpha-granule disorders

This chapter summarizes research data contributing to current understanding of disorders affecting alpha-granules of megakaryocytes and platelets. Diagnostic features of the gray platelet syndrome are well defined. Combined evidence suggests a defect, specific to the megakaryocyte cell lineage, causing a cytoskeletal abnormality and defective targeting of endogenously synthesized proteins to the alpha-granule. The abnormalities linked by signal transduction pathways. von Willebrand disease and afibrinogenaemia are disorders which highlight the functional importance of platelet storage pools of von Willebrand factor and fibrinogen, essential ligands in the process of adhesion and aggregation. The abnormality in the factor V Quebec disorder leads to a degradation of most proteins contained within the alpha-granule. The familial platelet disorder Paris-Trousseau thrombocytopenia is the only alpha-granule disorder associated with a cytogenetic abnormality, and it presents a useful model for exploring the genetic influence on regulation of thrombopoiesis. Study of these syndromes has elucidated aspects of the physiology of normal megakaryocyte maturation and platelet formation, including storage organelle biosynthesis.

Platelet membrane receptors during short cardiopulmonary bypass--a flow cytometric study

To elucidate a mechanism of platelet dysfunction during extracorporeal circulation, we performed a study on the surface expression of platelet adhesive receptors (GPIb, GPIIb-IIIa) and activation markers (GMP140, GP53) during short cardiopulmonary bypass (CPB). Ten paediatric patients, age 6-13 years, with atrial or atrioventricular septal defects were studied. The mean CPB time was 52 min (21-110 min). During CPB, a significant drop in platelet count was observed, but not below 130 x 10(3)/microliter. The expression of platelet GPIb decreased slightly during CPB and the decrease was not significant. The decrease of GPIIb-IIIa was significant, but only in samples collected either at the end of CPB (89 +/- 13%, p < 0.05) or before leaving the operating room (74 +/- 14%, p < 0.05). The value of surface expression of platelet activation markers (GMP140, GP53) during CPB was in the range of values for resting platelets. Our results suggest that generalized CPB-induced defects of primary haemostasis are not directly connected to circulation of activated degranulated platelets or to loss of platelet adhesive receptors GPIb-IX and GPIIb-IIIa.

Identification of a domain (155-183) on CD36 implicated in the phagocytosis of apoptotic neutrophils

Clearance of apoptotic neutrophils by macrophages is a crucial event following the resolution of acute inflammation. CD36, together with alphavbeta3, has been identified as one of the adhesion molecules on the surface of macrophages implicated in the clearance of polymorphonuclear leukocytes. The domain on CD36 implicated in the phagocytosis of aged neutrophils remains to be elucidated. In this study, COS cells transfected with human CD36 cDNA had a significantly higher capacity to phagocytose human apoptotic neutrophils compared with murine CD36 cDNA. Moreover, monoclonal antibodies 10/5 or OKM5 (epitopes identified on amino acids 155-183) but not monoclonal antibody 13/10 (epitope identified on amino acids 30-76) inhibited phagocytosis of apoptotic neutrophils by COS cells transfected by human CD36. Swapping the human CD36 155-183 domain from human to murine CD36 (human-murine CD36 chimera) imparted to murine CD36-transfected COS cells an increased capacity to phagocytose apoptotic neutrophils. Conversely, when the murine domain 155-183 was inserted in human CD36, a decreased phagocytic capacity was observed. In addition, a synthetic peptide(155-169) but not its scrambled form significantly inhibited phagocytosis. These results identify for the first time a functional domain encompassing amino acids 155-183 on human CD36 implicated in the recognition and phagocytosis of apoptotic neutrophils.

Factors influencing haemostasis and blood transfusion in cardiac surgery

To find out the risk factors influencing perioperative bleeding and use of blood products in cardiac surgery so that appropriate interventions can be selected for blood conservation, risk factors were analysed in 343 cardiac surgical patients, retrospectively, by multiple regression technique. The results showed that the factors related to postoperative bleeding were male gender, Higgins score, cardiopulmonary bypass (CPB) time, operation procedures, intraoperative blood loss and use of internal mammary artery (IMA) graft. Factors related to perioperative homologous blood transfusions were emergency surgery, preoperative haemoglobin level, Higgins score, intraoperative blood loss, operation time and operation procedures. The geometric mean of postoperative bleeding in the entire series was 1085 ml and the mean packed red cell, plasma and platelet transfusions were 3.29 +/- 0.4, 1.96 +/- 0.39 and 0.21 +/- 0.05 units respectively. The incidence of homologous blood transfusion during the hospital stay was 58.9% for the entire series and 54.5% in the nonrevision patients. Emergency patients received significantly more blood transfusion (p = 0.0001). Perioperative blood loss and transfusions are still problems in cardiac surgery and certain patient groups in this study were identified as high risk; available blood conservation techniques, therefore, are recommended in these patients.

Maintaining blood flow in the extracorporeal circuit: haemostasis and anticoagulation

OBJECTIVES

To review the methods and developments in maintaining extracorporeal circuits in critically ill patients.

DESIGN

The review includes details of the pathophysiological processes of haemostasis and coagulation in critically ill patients, methods of maintaining blood flow in the extracorporeal circuit and methods of monitoring anticoagulation agents used.

SETTING

Information is relevant to the management of critically ill patients requiring extracorporeal renal and respiratory support and cardiopulmonary bypass.

CONCLUSIONS

Heparin is the mainstay of anticoagulation for the extracorporeal circuit although the complex abnormalities of the coagulation system in critically ill patients are associated with a considerable risk of bleeding. Alternative therapeutic agents and physical strategies (prostacyclin, low molecular weight heparin, sodium citrate, regional anticoagulation, heparin bonding and attention to circuit design) may reduce the risk of bleeding but expense and difficulty in monitoring are disadvantages.

Aprotinin in perspective

Aprotinin is a nonspecific serine protease inhibitor extracted from bovine lung. It was first used during cardiopulmonary bypass to inhibit plasmin-induced complement activation. By chance significant reductions of blood loss and blood requirements were noted in treated patients. Subsequent investigation showed improved hemostasis to result from protection of platelet adhesive receptors (Gp Ib) at the onset of cardiopulmonary bypass. Without aprotinin the contact system of plasma is massively activated on first passage through the cardiopulmonary bypass circuit. Activation of the intrinsic coagulation pathway causes thrombin formation, which impairs platelet adhesive function. Aprotinin blocks contact activation of the kallikrein system during cardiopulmonary bypass and in synergy with heparin prevents thrombin formation through inhibition of the intrinsic clotting cascade. It is likely that neither thrombin nor platelets become involved in the blood-foreign surface contact activation process in aprotinin-treated patients. The fact that the hemostatic process is affected from the very beginning of cardiopulmonary bypass is substantiated by the fact that low-dose aprotinin therapy (2 x 10(6) KIU aprotinin added to the pump prime) leads to the same preservative effect on Gp Ib receptors and blood loss as continuous high-dose infusion (6 x 10(6) KIU) throughout the whole surgical procedure. In the presence of heparin aprotinin prolongs the activated clotting time and the in vitro activated partial thromboplastin time. This has important implications for heparin dosage. An inhibitory effect on the endothelial cell anticoagulant function may also have consequences during hypothermic low flow and circulatory arrest states.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma protein adsorption to hemodialysis membranes: studies in an in vitro model

Upon interaction of whole blood with foreign materials, heterogeneous protein films are deposited onto the artificial surface (eg, hemodialysis membranes). The composition of these protein films subsequently affects various processes, eg, thrombogenesis or activation of the complement system. We developed an in vitro model with which we can identify and study proteins interacting with capillaries during hemodialysis. Using this model we studied the cuprophane dialyzer GFS 120 (CP) and the polymethylmetacrylate membrane Filtryzer B2-1.2 (PMMA). Heparinized whole blood from healthy young volunteers was dialyzed on an extracorporeal dialysis machine. After the dialysis procedure the adsorbed material was eluted from the hemodialysis membranes by different eluants and subsequently analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. A number of proteins could be identified in the eluates of both membrane types. Interestingly, platelet glycoproteins could only be found in PMMA eluates. Albumin, IgG, and antithrombin III were mainly present in the cuprophane eluates. Fibrinogen was demonstrable in all eluates, but in relatively low amounts, and the protein was significantly degraded. Degradation products of antithrombin III and complement factor 3 could also be identified. The process causing the degradation has not yet been identified, but may be due to proteases released from damaged cells.

Platelet protection by aprotinin in cardiopulmonary bypass: electron microscopic study

To evaluate the functional integrity of platelets in patients administered the proteinase inhibitor aprotinin during cardiopulmonary bypass, 20 patients undergoing a complicated and prolonged open heart operation were studied. They were randomized to receive either a high dose of aprotinin (total dose, 6 to 7 x 10(6) KIU) before and during cardiopulmonary bypass (10 patients) or a placebo (10 patients). Blood samples were collected preoperatively, at the termination of bypass, and 90 minutes thereafter to assess platelet count and aggregation on extracellular matrix, which was studied by scanning electron microscopy. On a scale of 1 to 4, mean preoperative platelet aggregation grades were similar in both groups (3.5 +/- 0.5). Postoperatively, at the termination of cardiopulmonary bypass and 90 minutes thereafter, all 10 patients treated with aprotinin revealed normal, unchanged platelet aggregation (grade, 3.5 +/- 0.5), whereas all placebo-treated patients showed severely disturbed aggregation (grade, 1.4 +/- 0.5) (p less than 0.001). The platelet count was similar in both groups before and after operation (preoperatively, 182 +/- 75 x 10(9)/L and 146 +/- 30 x 10(9)/L, and postoperatively, 87 +/- 13 x 10(9)/L and 80 +/- 27 x 10(9)/L for the aprotinin and placebo groups, respectively). Total 24-hour postoperative bleeding and blood requirement were significantly lower in the aprotinin group (371 +/- 84 mL and 2 +/- 0.7 units, respectively) compared with the placebo group (608 +/- 28 mL and 3.4 +/- 1.3 units, respectively) (p less than 0.01). These results demonstrate that improved postoperative hemostasis is directly related to the complete preservation of platelet function achieved by the protective properties of aprotinin.

An abnormal pattern of multiple platelet function abnormalities and increased thromboxane generation in patients with primary thrombocytosis and thrombotic complications

Platelet aggregation (PA) induced by ADP, collagen and epinephrine, plasma levels of beta-thromboglobulin (beta TG) and thromboxane B2 (TXB2) and serum TXB2 generation were studied in 11 patients with primary thrombocytosis (7 with essential thrombocythaemia and 4 with polycythaemia vera) and compared with 16 healthy subjects. 5 patients suffered from peripheral vascular ischaemia and another 3 had venous thrombosis, but none had bleeding complications. The patients showed an abnormal pattern of platelet function and of thromboxane generation distinct from the healthy subjects in three aspects. a) Shape change was 5-26 times greater, the lag-time of collagen PA was 2.3-2.9 times longer and the extent of epinephrine PA was nil or very low. ADP- or collagen-induced PA was also reduced (p less than 0.02). b) Plasma TXB2 generation (corrected to a normal platelet concentration) stimulated by the three PA inducers was within the range of the healthy subjects in spite of the reduced extent of PA. c) Plasma beta TG level and serum TXB2 generation (both corrected to a normal platelet concentration) were 2.9-7.1 times higher (p less than 0.001) indicating enhanced in vivo platelet activation and possibly increased thrombin generation. These abnormalities were not detected in another 4 patients with secondary thrombocytosis. The abnormal pattern of platelet function and thromboxane generation can be a useful laboratory method in the evaluation of patients with primary thrombocytosis. It might also explain the thrombotic complications which occurred in 8 of the patients in a manner such that increased or normal TXB2 generation overcomes the reduced extent of PA. In this respect, the pronounced serum TXB2 synthesis might be a marker of intravascular thrombosis.

Inhibition of fibrin(ogen) binding to stimulated platelets by a monoclonal antibody specific for a conformational determinant of GPIIIa

We have purified the integrin GPIIb:IIIa from the membrane fraction of human blood platelets by lentil lectin affinity chromatography followed by gel filtration chromatography. With purified GPIIb:IIIa as an antigen, we have produced monoclonal antibody CS-1, which immunoblotting demonstrates to be specific for native GPIIIa; disulfide bond reduction of GPIIIa resulted in loss of immunoreactivity. Radiolabelled ligand binding studies revealed that CS-1 recognized approximately 55,000 sites per platelet and bound with a Kd in the nanomolar range, independent of the state of platelet activation. Binding of CS-1 or its Fab fragment to ADP- and thrombin-stimulated gel filtered platelets caused a 2-3 fold inhibition of binding the soluble ligands fibrinogen and fibrin protofibrils. CS-1 also inhibited aggregation of ADP- and thrombin-stimulated platelets by 2- and 4-fold, respectively. Since CS-1 inhibits fibrin(ogen) interactions with GPIIb:IIIa, we propose that the conformationally dependent epitope on GPIIIa recognized by CS-1 constitutes a region of the receptor which is involved in fibrin(ogen) binding.

Decreased stability and structural heterogeneity of the residual platelet glycoprotein IIb/IIIa complex in a variant of Glanzmann's thrombasthenia

A patient is described with a disturbance of platelet function comparable to that in Glanzmann's thrombasthenia. Platelet aggregation and binding of fibrinogen to the patient's platelets were defective and thrombin-induced clot retraction was absent. The platelet fibrinogen content was only moderately reduced. As measured by monoclonal antibody binding in the presence of divalent cations, the platelets contained about 15% of the normal amount of GPIIb and GPIIIa and only 6% of the normal amount of intact GPIIb/IIIa complex. The residual GPIIb/IIIa complex exhibited a decreased stability as shown by the lack of binding of a complex-dependent anti-GPIIb/IIIa antibody to platelets incubated with ethylene diamine tetraacetic acid (EDTA) at 22 degrees C. Crossed immunoelectrophoresis (CIE) in the presence of divalent cations showed partial dissociation of GPIIb/IIIa as well as the presence of two forms of the residual intact GPIIb/IIIa complex. In addition, both CIE in the presence of the EDTA and two-dimensional sodium dodecyl sulphate (SDS) gel electrophoresis showed the presence of two forms of GPIIb. This form of thrombasthenia is characterized by a defective platelet function, a marked reduction of GPIIb and GPIIIa, decreased stability of the residual GPIIb/IIIa complex and structural heterogeneity of GPIIb.