Severe HPA-15b related neonatal alloimmune thrombocytopenia.

UNLABELLED: The HPA-15 platelet (PLT) group was recently described. Severe neonatal thrombocytopenia due to alloimmunization by HPA-15b has very rarely been observed. A 22-year-old mother, gravida 1/para 1, gave birth to a male infant who presented with a severe thrombocytopenia, the PLT count recorded to be 3 x10(9)/L. A few hours after birth, he developed purpura with extensive haematomas but without visceral or intracranial haemorrhage (ICH). Two PLT transfusions were given including one using maternal PLTs. The infant's PLT count was 267 x 10(9)/L on day 6. The maternal platelet group was HPA-15a/a and her infant was HPA-15a/b. Anti-HPA-15b antibodies was found in maternal serum. CONCLUSION: HPA-15b maternal alloimmunization may induce severe neonatal thrombocytopenia. In order to establish the frequency of neonatal alloimmune thrombocytopenia (NAIT) due to anti-HPA-15b antibodies, an improved detection method is necessary.

The effects of methylprednisolone on complement-mediated neutrophil activation during cardiopulmonary bypass.

Complement-mediated neutrophil activation (CMNA) has been implicated as an important pathophysiologic mechanism contributing to acute microvascular lung injury in the adult respiratory distress syndrome (ARDS). Using cardiopulmonary bypass (CPB) as a clinical model for complement-mediated microvascular injury, we studied the effects of methylprednisolone (MPSS) pretreatment on manifestations of CMNA in 28 pediatric patients undergoing CPB. Six patients not receiving MPSS served as controls. Results demonstrated that MPSS did not prevent complement activation as noted by 4.5- and 7.7-fold increases in plasma C3a des Arg levels during and immediately after CPB, respectively. However, detectable in vivo and in vitro manifestations of CMNA were altered. Neutropenia during CPB was attenuated to 65% of prebypass values compared with 47% in the control group. Neutrophil selective chemotactic desensitization toward C5a/C5a des Arg during the on bypass and postbypass periods was evident in the control group (0.41 and 0.76 cm specific migration, respectively) and prevented in the MPSS group (1.55 and 2.00 cm specific migration, respectively). We conclude that CMNA during CPB is ameliorated and/or prevented by MPSS pretreatment. These findings suggest that MPSS pretreatment may ameliorate complement-mediated microvascular (lung) injury in CPB and ARDS.

Complement activation and clearance in acute illness and injury: evidence for C5a as a cell-directed mediator of the adult respiratory distress syndrome in man.

The appearance of the adult respiratory distress syndrome (ARDS) during the course of acute illness is believed to result, in part, from intrapulmonary neutrophil sequestration and degranulation induced by circulating inflammatory mediators. To evaluate the role of complement-neutrophil interactions in the pathogenesis of ARDS in man, 34 patients suffering from intra-abdominal sepsis (seven), multisystem trauma (15), or acute pancreatitis (12) were serially studied with regard to neutrophil migratory responses to C5a and F-Met-Leu-Phe, lysosomal content of beta-glucuronidase and lysozyme, and simultaneously obtained plasma levels of immunoreactive C3adesArg and C5adesArg. Nineteen patients developed ARDS. In these patients, plasma C3adesArg levels obtained within 72 hours of admission to the hospital were elevated to 305 +/- 35 ng/ml compared with 145 +/- 16 ng/ml for patients who did not develop ARDS (p less than 0.0005). C5adesArg levels were not elevated in either group. In vitro studies showed that neutrophils from normal persons were able to clear all of the C5a/C5adesArg generated in up to 5% zymosan-activated serum, while no clearance of C3adesArg was identified. Patient migratory responses could be divided into three groups based on their initial (less than 72 hour) samples: (1) hyperresponsive to both N = formyl-methionyl-leucyl-phenylalanine (FMLP) and C5a, (2) specifically deactivated to C5a, and (3) deactivated to both C5a and FMLP. Patients in the latter two groups developed ARDS. Enzyme content of neutrophils from patients who developed ARDS showed a substantial fall in beta-glucuronidase and lysozyme levels. The finding of elevated plasma C3a levels and deactivation of migratory response to C5a support the contention that complement activation had occurred in these patients and that their neutrophils had been exposed to C5a/C5adesArg in vivo. The finding of nonspecific migratory dysfunction associated with lysozymal enzyme loss, a circumstance not reproducible in vitro by C5a exposure, suggests that other stimuli produced degranulation of neutrophils made hyperresponsive by prior exposure to C5a.

Regulation of neutrophil superoxide production in sepsis.

Neutrophil superoxide production has been recognized as an important pathway for microbicidal activity and regulation of the local inflammatory environment. To investigate neutrophil superoxide production in sepsis, we studied 22 patients with intra-abdominal infections, and correlated superoxide production with chemotactic response and granular enzyme content. Our results showed that neutrophils from infected patients had specific loss of chemotactic response to C5a, and were deficient in the granular enzymes, lysozyme, and beta-glucuronidase. Superoxide production in response to opsonized zymosan was intact, but response to the chemoattractant N-formyl-methionyl-leucyl-phenylalanine was markedly depressed. This could be reversed in vitro by the addition of cytochalasin B. These results suggest that down regulation of exocytosis of superoxide to nonphagocytic stimuli occurs during sepsis, possibly protecting the host from tissue injury due to oxide radical release. Superoxide response to phagocytic stimulation was intact.

Complement-induced expression of cryptic receptors on the neutrophil surface: a mechanism for regulation of acute inflammation in trauma.

We explored the hypothesis that identified changes in neutrophil function in patients with acute injury result from in vivo exposure to C5a. To evaluate this hypothesis, we performed a battery of tests on 26 trauma patients (14 with blunt injury, 12 with penetrating injury). Measured were plasma levels of the complement activation products C3a and C5a; neutrophil chemotaxis to C5a and N-formyl-methionyl-leucyl-phenylalanine (FMLP); neutrophil receptors for FMLP and C3b; and superoxide response to FMLP and serum-opsonized zymosan. Patient responses measured within 48 hours of admission were divided into two groups based on neutrophil migratory response to C5a. Patients unresponsive to C5a (but responsive to FMLP) showed elevated plasma C3a levels (248 +/- 6 ng/ml) compared with patients with normal C5a migratory response (104 +/- 8 ng/ml). FMLP receptor number was markedly increased in the chemotactically deactivated group (group I: 155,680 +/- 100; group II: 51,200 +/- 200) and receptor affinity was diminished. Binding activity of C3b increased in the C5a-unresponsive cells to 126% that of controls versus 94% for normally responsive patient cells. Superoxide production was found to be significantly increased in patient cells with increased receptor numbers. These results support the concept that a subgroup of trauma patients manifest plasma and neutrophil changes compatible with complement activation. The neutrophil changes identified demonstrate a state of cellular activation. The clinical significance of these results may reside in a risk of pulmonary microvascular injury if activated cells are marginated and then subsequently stimulated.

Neutrophil dysfunction in sepsis. III. Degranulation as a mechanism for nonspecific deactivation.

Prominent and global abnormalities in chemotactic, oxidative, and microbicidal activity have been identified in neutrophils from patients with severe sepsis. To evaluate the possible contribution of degranulation as the basis for the observed abnormalities, 12 patients with intrabdominal infection were serially studied and neutrophil chemotaxis, enzyme content, and receptors for FMLP were evaluated. There was a significant correlation between chemotactic response to both activated serum and FMLP with the granular enzymes beta-glucuronidase and lysozyme. For FMLP-directed migration, r = 0.73, P less than 0.001 for lysozyme, and r = 0.59, P less than 0.001 for beta-glucuronidase. There was a similarly significant correlation between loss of lysozyme and an increase in FMLP receptors, previously shown to be a marker for degranulation. These data support the concept that in vivo degranulation, possibly due to effects of circulating chemoattractants on adherent neutrophils, is responsible for the enzymatic and chemotactic loss seen in cells from septic patients. This hypothesis also provides a mechanism to explain the respiratory distress syndrome if degranulation were to occur in the pulmonary capillary bed.