Association of the high-affinity receptor for IgG (Fc gamma RI) with the gamma subunit of the IgE receptor

How receptors for the Fc portion of IgG antibodies (Fc gamma R) trigger a variety of immune functions by clustering upon engagement of ligand is largely unknown. Of the three distinct classes of human Fc gamma R, only Fc gamma RIIIA has been shown to associate with a potential signal-generating subunit, either the gamma chain or the zeta chain. With these studies we show that Fc gamma RI, the high-affinity receptor for IgG, also is found in association with gamma chain. This association can be demonstrated by using anti-Fc gamma RI antibodies, Fc gamma RI ligand, and anti-gamma-chain antibodies that coadsorb the proteins from detergent lysates of Fc gamma RI-expressing cells. The association of Fc gamma RI and gamma chain can be reconstituted by cotransfection of cDNAs for both proteins into COS cells.

Implementing modular nursing in a long-term care facility

Nurse administrators in long-term care are challenged to maintain the quality of nursing care under constant fiscal and staffing pressures. Restructuring nursing care delivery is one method often used to meet this challenge. The authors describe their experience of implementing a nursing care delivery model that resulted in improved continuity of care, accountability for client outcomes, and the effective use of different staff levels.

J5 prevents endotoxin shock in suckling rats

A sublethal dose of endotoxin (lipopolysaccharide: LPS) can induce endotoxin tolerance. It is not well known whether LPS feeding causes endotoxemia and endotoxin tolerance in the newborn. Since Rc mutant Escherichia coli LPS (J5) does not have toxic or lethal effects, J5 is used to induce endotoxin tolerance in this study. This study showed that both an intraperitoneal (ip) injection and feeding of Rc mutant Escherichia coli LPS (J5) induced endotoxin tolerance in suckling rats.

Epidemiological aspects of fatal and severe injury urban freeway crashes

Two types of crashes are common on urban freeways: in-lane rear-end impacts with stopped or slowed vehicles and those where a vehicle leaves the roadway (and road shoulder) and impacts with obstacles outside traffic lanes. Crashes resulting in a fatal or severe injury to a vehicle occupant were identified from crash records in the regional office of the California Department of Transportation for the 1,500 miles of freeways in Los Angeles, Ventura, and Orange counties, California, for 1984 and 1985. Selected road characteristics were assessed and traffic-volume data obtained for these freeways to determine the relationship of these types of crashes to freeway features. Fatal- or severe-injury crash rates were highest for off-road crashes compared with in-lane crashes, with certain lanes having more frequent in-lane collisions and with a higher rate of in-lane crashes in freeway segments without a left shoulder. Off-road collisions were significantly more frequent in the absence of a right shoulder and on freeways with two or three lanes. Multivariate analyses that control for selected confounding factors such as traffic volume show similar findings including strong association with hour of crash.

Evolution of the Adh locus in the Drosophila willistoni group: the loss of an intron, and shift in codon usage

We report here the DNA sequence of the alcohol dehydrogenase gene (Adh) cloned from Drosophila willistoni. The three major findings are as follows: (1) Relative to all other Adh genes known from Drosophila, D. willistoni Adh has the last intron precisely deleted; PCR directly from total genomic DNA indicates that the deletion exists in all members of the willistoni group but not in any other group, including the closely related saltans group. Otherwise the structure and predicted protein are very similar to those of other species. (2) There is a significant shift in codon usage, especially compared with that in D. melanogaster Adh. The most striking shift is from C to U in the wobble position (both third and first position). Unlike the codon-usage-bias pattern typical of highly biased genes in D. melanogaster, including Adh, D. willistoni has nearly 50% G + C in the third position. (3) The phylogenetic information provided by this new sequence is in agreement with almost all other molecular and morphological data, in placing the obscura group closer to the melanogaster group, with the willistoni group farther distant but still clearly within the subgenus Sophophora.

Extremely low birth weight children and their peers: a comparison of preschool performance

Though not well studied, extremely low birth weight (ELBW; < 1000 g) appears to be a major risk factor for developmental disability, with most affected children experiencing school problems (40% to 64%) rather than severe handicap (25%). This study marks the first published US attempt to document prospectively the developmental/educational progress of a cohort of predominantly white, middle-class ELBW children with randomly selected and matched heavier birth weight (1500 through 2500 g and > 2500 g) peer comparison groups. Sixty ELBW children and 60 peers were administered a test battery at age 4 years, including the McCarthy Scales of Children's Abilities, Peabody Picture Vocabulary Test, and Beery Test of Visual-Motor Integration. The ELBW group mean scores were significantly lower than those of the peer groups on every measure, although generally still within 1 SD of the test mean. Twenty-three percent were clearly disabled; 26% had optimal development, having attained at least average scores on all measures; and 51% attained borderline scores globally or had an average cognitive score, but specifically poor performance in one or more areas. Comparison groups were 2 1/2 times more likely to have optimal development and had mean cognitive scores 15 to 18 points higher than the ELBW group. In summary, weaker performance on all measures exists prior to school entry among nondisabled ELBW children compared with their peers. It is unclear whether these data portend emerging school-based disabilities or describe a continuing recovery process to be completed in middle childhood. Continued follow-up of this cohort at 7 and 10 years of age will address these questions.

Intact survival of a 280-g infant: an extreme case of growth retardation with normal cognitive development at two years of age

The care of infants born weighing less then 500 g is not only controversial but is also associated with medical uncertainties. We report the management of a growth retarded infant who weighed 280 g at birth after 26.9 weeks' gestation. The child not only survived but appears developmentally normal at two years of age. Although the infant is the smallest survivor reported, the case demonstrates the importance of gestational assessment in deciding delivery room management.

Three genes for the human high affinity Fc receptor for IgG (Fc gamma RI) encode four distinct transcription products

Three distinct but closely related classes of receptors that bind the Fc portion of immunoglobulin G (Fc gamma RI, -II, and -III) have been identified in humans. Only Fc gamma RI has high affinity for ligand and has a unique third extracellular domain (EC3). We have characterized three genes for human Fc gamma RI (A, B, and C). Each gene consists of six exons, spans 9.4 kilobase pairs, and localizes to chromosome 1. Although they are remarkably similar, genes B and C are notably different from A; in-frame stop codons are present in the EC3 domain of genes B and C, and deletions occur in a splice donor sequence of gene B. Four distinct Fc gamma RI transcripts were analyzed. One transcript, from gene A, would encode a transmembrane receptor with three external domains. A second transcript, an alternatively spliced product of gene B, would encode a two-external domain transmembrane receptor. Two transcripts, from genes B and C, have stop codons in EC3 and would be predicted to generate secreted receptors.

Effects of dexamethasone on the hypothalamic-pituitary-adrenal axis in preterm infants

The effects of dexamethasone therapy on the hypothalamic-pituitary-adrenal axis were tested in 10 premature infants with bronchopulmonary dysplasia by means of the corticotropin-releasing hormone stimulation test before therapy and on the seventh day of therapy. Adrenocorticotropic hormone and cortisol levels were determined by radioimmunoassay. There was significant suppression of the hypothalamic-pituitary-adrenal axis after 7 days of a currently used dexamethasone treatment regimen. A site of suppression was located at the level of the pituitary gland.

Early endotoxin tolerance in suckling rats

Early endotoxin tolerance has not been well investigated in the newborn. This study demonstrated that a sublethal dose of Salmonella enteritidis lipopolysaccharide (S. ent-LPS) or rough mutant Salmonella minnesota LPS (Re-LPS) induced early endotoxin tolerance in suckling rats, showing blunted hypoglycemia and decreased mortality. The mortality of endotoxic shock was lower in S. ent-LPS pretreated group than Re-LPS pretreated group. A sublethal dose of S. ent-LPS caused lactacidemia but Re-LPS did not. Therefore, early endotoxin tolerance appeared to be related to physiologic responses to the initial LPS exposure.

Cord blood thyrotropin screening for congenital hypothyroidism. Three years' experience on the Island of Saint Lucia

Cord blood thyrotropin (TSH) screening for congenital primary hypothyroidism has been in effect on the island of St. Lucia for the past three years. Umbilical cord blood samples are obtained on Guthrie filter paper and then transported 3,000 miles to Loyola University of Chicago and delivered to the Illinois State Metabolic Screening Laboratory. There TSH is measured by radioimmunoassay (RIA). After three years, 1,789 newborns have been screened, and the mean value is 6.23 +/- 0.13 microIU per ml. This mean value is less than previously reported by us in 1986 (10.23 +/- 0.29 microIU per ml).13 It is concluded that this screening service continues to be possible far removed from the population under observation. No case of primary hypothyroidism has been detected. Our decreased mean TSH value is due to the new method currently used by the Illinois State Metabolic Screening Laboratory. Congenital hypothyroidism will not be missed provided internal controls are established and rigidly observed.

Anti-GPIIb/IIIa (CD41) monoclonal antibody-induced platelet activation requires Fc receptor-dependent cell-cell interaction

We studied platelet activation by UR1, a murine IgG1 anti-CD41 mAb. Like thrombin and crosslinked anti-Fc gamma RII mAb IV3, UR1 initiates prompt aggregation and Ca2+ mobilization. UR1 F(ab')2 fragments failed to activate, yet inhibited UR1 IgG-mediated activation. UR1-induced activation was blocked by anti-Fc gamma RII mAb. High viscosity (15% dextran or Ficoll), which impedes cell-cell interaction, inhibited activation by UR1. Cell-cell interaction was confirmed by cell-mixing studies. UR1 binding to platelets of one pool was blocked with UR1 F(ab')2 allowing UR1 binding only to Fc gamma RII. IV3 Fab fragments blocked ligand binding to Fc gamma RII on platelets of a second pool; thus, UR1 could bind only its epitope. UR1 initiated an immediate [Ca2+]i increase in the intermixed pools at low ionic strength. These studies indicate that UR1 IgG binds CD41 on one platelet to form immune complexes which then crosslink and stimulate Fc gamma RII on nearby platelets. Two other anti-CD41 mAb, 6C9 and C17, and two anti-CD9 mAb, AG1 and mAb7, activated platelets in a UR1-like manner. We propose that platelet Fc gamma RII crosslinking that follows the interaction of IgG-opsonized platelets may be a common mechanism by which anti-platelet antibodies activate platelets.

Gene organization of the human high affinity receptor for IgG, Fc gamma RI (CD64). Characterization and evidence for a second gene

We have isolated, characterized, and sequenced the gene coding for the 72-kDa human high affinity IgG FcR, hFc gamma RI. It consists of six exons and spans 9.4 kilobase pairs. The leader sequence is encoded by two exons, the second of which is 21 base pairs long and contains the predicted site of peptidase cleavage. The third, fourth, and fifth exons each encode homologous Ig-like extracellular domains. The hydrophobic transmembrane region and a highly charged cytoplasmic tail are encoded by a single final exon. The sequence of the 5'-flanking region was determined. Two major transcription initiation sites were identified by RNase protection. The first, more downstream site was confirmed by primer extension studies; canonical CAAT and TATA boxes are located in appropriate positions upstream from this site. The second transcription initiation site was utilized only in RNA from cells incubated with gamma-interferon. This site initiates transcription upstream from the first major site. These data are consistent with the finding of two species of mRNA for hFc gamma RI in myeloid cells that are upregulated when cultured with gamma-interferon. Southern analysis of genomic DNA confirms the restriction map generated from the cloned DNA. One additional HindIII fragment was observed in genomic DNA from 13 randomly selected individuals that was not present in the phage clone used to characterize the gene. This observation suggests the existence of a second hFc gamma RI gene which lacks one of the two internal HindIII sites rather than a restriction fragment length polymorphism.

Emerging developmental sequelae in the 'normal' extremely low birth weight infant

Thirty-six extremely low birth weight (less than 1000 g birth weight) children received neurodevelopmental testing in infancy (mean age = 19.1 months), and again in early childhood (mean age = 46.5 months). Children were categorized into a high-risk group (n = 20) if bronchopulmonary dysplasia and/or Grades III or IV intracranial hemorrhage were present or a low-risk group (n = 16) if neither were present. Using standardized testing and neuromotor examination, 24 (67%) of 36 children showed normal infant development. Only 11 (31%) of 36 children (P less than .005) had normal development upon reassessment in early childhood. A decline in developmental status occurred in both groups. This indicates that for the extremely low birth weight population, normal infant development is poorly predictive of continued normal development. With or without major complications, extremely low birth weight places children at substantial risk for ongoing and emerging developmental problems with age.

Identification and structural characterization of Fc gamma-receptors on pulmonary alveolar macrophages

Little is known about the structure of the cell surface receptors for the Fc portion of immunoglobulin G (Fc gamma R) on tissue macrophages. Studies on leukocytes indicate the existence of three classes of Fc gamma R, denoted I, II, and III. The purpose of this study was to structurally characterize Fc gamma R on alveolar macrophages obtained by bronchoalveolar lavage, comparing them with Fc gamma R of monocytes, neutrophils, and U937 cells. Flow-cytometric evaluation, utilizing anti-Fc gamma R class-specific monoclonal antibodies, showed that alveolar macrophages expressed three Fc gamma R classes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the immunopurified Fc gamma R molecules revealed the following apparent molecular mass for each Fc gamma R class: Fc gamma RI, 70 kDa; Fc gamma RII, 44 kDa; and Fc gamma RIII, 57-65 kDa. RNA blot analysis demonstrated a 1.7-kb transcript for Fc gamma RI, 2.5 and 1.6 kb transcripts for Fc gamma RII, and a 2.2 kb mRNA for Fc gamma RIII. Fc gamma RII displayed the high-responder/low-responder polymorphism. Fc gamma RIII did not express the neutrophil antigen-type specific structural polymorphism of the deglycosylated Fc gamma R molecule and appeared to be a transmembrane molecule.

Signal transduction by the platelet Fc receptor

We have evaluated the mechanism by which crosslinking human platelet Fc receptor (FcR) for IgG triggers platelet aggregation and the platelet release reaction. Platelet FcR was crosslinked by incubating purified human platelets with anti-FcRII monoclonal antibody and F(ab')2 anti-mouse Ig. The resultant [Ca2+]i increase, monitored by Fura-2 and measured in the absence of extracellular Ca2+, reached a peak of 750 +/- 50 nmol/L. The effects of cyclooxygenase inhibitors, aspirin and indomethacin, and a phospholipase A2 inhibitor, dibromoacetophenone, were examined. Regardless of the inhibitor, at least 25% of the [Ca2+]i increase remained. Thrombin (0.2 U/mL) stimulated an immediate [Ca2+]i increase that reached 1.95 +/- 0.8 mumol/L. The [Ca2+]i increase generated by thrombin was only slightly reduced by these inhibitors. Crosslinking the FcRII of platelets resulted in a fivefold increase in the production of [3H]inositol phosphates, (IP) which, in the absence of extracellular Ca2+ was insensitive to aspirin. The activation of a [Ca2+]i increase along with the measured increases in IP indicate that FcRII crosslinking leads to the activation of phospholipase C (PLC). In contrast to thrombin, platelet activation via FcRII depends to a large extent on arachidonic acid metabolites. However, neither cyclooxygenase nor phospholipase A2 inhibitors completely blocked FcRII-stimulated [Ca2+]i increase. These observations led us to propose that crosslinking of platelet FcRII initially activates PLC.

Fatal and severe injury: scooter and moped crashes in California, 1985

Fatal and severe injury crashes for scooters and mopeds in California for 1985 were compared with those for motorcycles during the same year. Scooters had more than twice the injury crash rate of mopeds but one-half the rate of motorcycles. Age of injured drivers and crash patterns for scooters, mopeds, and motorcycles varied significantly.

Direct hyperbilirubinemia associated with chloral hydrate administration in the newborn

To test the hypothesis that chloral hydrate can cause direct hyperbilirubinemia (DHB) in the newborn, two retrospective analyses of the medical records of patients admitted to a neonatal intensive care unit during an 18-month period were conducted. In one analysis of 14 newborns who had nonhemolytic DHB, 10 did not have an identified cause of DHB, and all 10 had received chloral hydrate. In the second retrospective study, all newborns who received chloral hydrate were divided into groups according to whether or not DHB had developed. The newborns with DHB, compared with those without DHB, had received a higher total accumulative dose of chloral hydrate (1035 +/- 286 vs 183 +/- 33 mg/kg [+/- 1 SEM], respectively). In the patients with DHB, the direct serum bilirubin levels increased 6.8 +/- 0.8 days after the chloral hydrate administration began and resolved after the chloral hydrate was discontinued or markedly decreased. These data support the hypothesis that prolonged use of chloral hydrate in newborns can be associated with DHB.

Alveolar and peritoneal macrophages bear three distinct classes of Fc receptors for IgG

The FcR for IgG on the plasma membrane of cells of the mononuclear phagocyte system mediate a number of different biologic responses such as phagocytosis, pinocytosis, superoxide generation, and antibody-dependent cytotoxicity. In the interest of understanding the pathophysiology of these processes we have begun to characterize the FcR for IgG on two readily available sources of macrophages--the lung and the peritoneum--using antireceptor mAb. We find that all three of the distinct classes of FcR for IgG which have been described in man are present on both pulmonary and peritoneal macrophages. Most monocytes, we suggest, bear low numbers of Fc gamma RIII whereas a small subpopulation of monocytes expresses substantial numbers of Fc gamma RIII. Furthermore, we find that two different forms of Fc gamma RIII differ in their capacity to bind anti-Fc gamma RIII mab 3G8 in the presence of human IgG. Human IgG does not block the binding of mAb 3G8 to neutrophils, but it does block 3G8 binding to macrophages and large granular lymphocytes; this finding correlates with the expression of the two Fc gamma RIII genes, I and II, in man. Studies aimed at illuminating the molecular mechanisms of Fc gamma R-mediated processes in macrophages will require consideration of the receptors of all three classes.

Alveolar and peritoneal macrophages bear three distinct classes of Fc receptors for IgG

The FcR for IgG on the plasma membrane of cells of the mononuclear phagocyte system mediate a number of different biologic responses such as phagocytosis, pinocytosis, superoxide generation, and antibody-dependent cytotoxicity. In the interest of understanding the pathophysiology of these processes we have begun to characterize the FcR for IgG on two readily available sources of macrophages--the lung and the peritoneum--using antireceptor mAb. We find that all three of the distinct classes of FcR for IgG which have been described in man are present on both pulmonary and peritoneal macrophages. Most monocytes, we suggest, bear low numbers of Fc gamma RIII whereas a small subpopulation of monocytes expresses substantial numbers of Fc gamma RIII. Furthermore, we find that two different forms of Fc gamma RIII differ in their capacity to bind anti-Fc gamma RIII mab 3G8 in the presence of human IgG. Human IgG does not block the binding of mAb 3G8 to neutrophils, but it does block 3G8 binding to macrophages and large granular lymphocytes; this finding correlates with the expression of the two Fc gamma RIII genes, I and II, in man. Studies aimed at illuminating the molecular mechanisms of Fc gamma R-mediated processes in macrophages will require consideration of the receptors of all three classes.