The SH2-containing 5'-inositol phosphatase (SHIP) is tyrosine phosphorylated after Fc gamma receptor clustering in monocytes

Current models of Fc gamma R signal transduction in monocytes describe a molecular cascade that begins upon clustering of Fc gamma R with the phosphorylation of critical tyrosine residues in the cytoplasmic domains of Fc gamma RIIa or the gamma-chain subunit of Fc gamma RI and Fc gamma RIIIa. The cascade engages several other tyrosine-phosphorylated molecules, either enzymes or adapters, to manifest ultimately an array of biological responses, including phagocytosis, cell killing, secretion of a variety of inflammatory mediators, and activation. Continuing to assess systematically the molecules participating in the cascade, we have found that the SH2-containing 5'-inositol phosphatase (SHIP) is phosphorylated on tyrosine early and transiently after Fc gamma R clustering. This molecule in other systems, such as B cells and mast cells, mediates an inhibitory signal. We find that clustering of either Fc gamma RIIa or Fc gamma RI is effective in inducing SHIP phosphorylation, that SHIP binds in vitro to a phosphorylated immunoreceptor tyrosine-based activation motif, peptide from the cytoplasmic domain of Fc gamma RIIa in activation-independent fashion, although SHIP binding increases upon cell activation, and that Fc gamma RIIb and Fc gamma RIIc are not responsible for the observed SHIP phosphorylation. These findings prompt us to propose that SHIP inhibits Fc gamma R-mediated signal transduction by engaging immunoreceptor tyrosine-based activation motif-containing cytoplasmic domains of Fc gamma RIIa and Fc gamma RI-associated gamma-chain.

Protein interactions of Src homology 2 (SH2) domain-containing inositol phosphatase (SHIP): association with Shc displaces SHIP from FcgammaRIIb in B cells

Our recent studies revealed that the inositol phosphatase Src homology 2 (SH2) domain-containing inositol phosphatase (SHIP) is phosphorylated and associated with Shc exclusively under negative signaling conditions in B cells, which is due to recruitment of the SHIP SH2 domain to the FcgammaRIIb. In addition, we reported that SHIP-Shc interaction involves both SHIP SH2 and Shc phosphotyrosine binding domains. These findings reveal a paradox in which the single SH2 domain of SHIP is simultaneously engaged to two different proteins: Shc and FcgammaRIIb. To resolve this paradox, we examined the protein interactions of SHIP. Our results demonstrated that isolated FcgammaRIIb contains SHIP but not Shc; likewise, Shc isolates contain SHIP but not FcgammaRIIb. In contrast, SHIP isolates contain both proteins, revealing two separate pools of SHIP: one bound to FcgammaRIIb and one bound to Shc. Kinetic studies reveal rapid SHIP association with FcgammaRIIb but slower and more transient association with Shc. Affinity measurements using a recombinant SHIP SH2 domain and phosphopeptides derived from FcgammaRIIb (corresponding to Y273) and Shc (corresponding to Y317) revealed an approximately equal rate of binding but a 10-fold faster dissociation rate for FcgammaRIIb compared with Shc phosphopeptide and yielding in an affinity of 2.1 microM for FcgammaRIIb and 0.26 microM for Shc. These findings are consistent with a model in which SHIP transiently associates with FcgammaRIIb to promote SHIP phosphorylation, whereupon SHIP binds to Shc and dissociates from FcgammaRIIb.

Differences between pickup truck and automobile driver-owners

This study compares pickup truck driver-owners and drivers who owned only automobiles with respect to demographic factors, conditions of use, risk-taking driving behavior, prior driving history and attitudes towards motor vehicle laws. A telephone survey conducted in Riverside County, CA determined that 36% of the households had a pickup truck. Pickup truck owners were primarily male, aged 30-39 years, married, reported lower restraint use and more risky driving behaviors, and had more traffic citations. Differences in behaviors and attitudes were largely a function of age and gender. There is a need to design appropriate occupant safety interventions for those most likely to own pickup trucks.

Molecular characterization of six variant Fcgamma receptor class I (CD64) transcripts

In humans, three distinct but closely related classes of receptors that bind the Fc portion of IgG (FcgammaRI, II and III) have been identified. FcgammaRI can bind monomeric IgG with high affinity and has a unique third extracellular domain (EC3). Three very similar genes have been characterized for FcgammaRI (A, B, C). Although the sequences are remarkably similar, a number of coding-region differences discriminate between the genes and amongst their transcripts. Six distinct FcgammaRI transcripts were analysed. Three transcripts, one from each gene, contain all six exons. Only the gene A transcript appears to encode a bona fide high affinity receptor, a three Ig-domain membrane spanning receptor that can bind monomeric IgG. Stop codons in the EC3 domains of the gene B and gene C isoforms would be predicted to generate secreted receptors. Three transcripts are alternatively spliced isoforms, one from gene A and two from gene B. One gene B transcript encodes a two Ig-domain transmembrane receptor which has structural characteristics of a low affinity FcgammaR.

Chimeric receptors composed of phosphoinositide 3-kinase domains and FCgamma receptor ligand-binding domains mediate phagocytosis in COS fibroblasts

Receptors for the Fc portion of IgG (FcgammaR) initiate phagocytosis of IgG-opsonized particles by a process involving the assembly of a multi-molecular signaling complex. Several members of this complex have been identified, including Src family kinases, Syk/ZAP 70 family kinases, and phosphoinositide 3-kinase (PI3-K). To test directly the role of PI3-K in mediating phagocytosis, we assessed the phagocytic ability of chimeric receptors composed of FcgammaR extracellular and transmembrane domains fused to regions of the p85 subunit of PI3-K. We found that chimeric receptors with cytoplasmic tails composed of the entire p85 subunit of PI3-K or the inter-Src homology 2 portion of p85 triggered phagocytosis in transfected COS fibroblasts. These two chimeras also showed phosphoinositide kinase activity in vitro when immunoadsorbed. In contrast, a chimera containing only the carboxyl-terminal Src homology 2 domain of p85 that does not interact with the catalytic p110 subunit of PI3-K did not trigger phagocytosis, nor did it show kinase activity in vitro. These data suggest that localization and direct activation of PI3-K at the site of particle attachment is sufficient to trigger the process of phagocytosis.

Family, social, and cultural factors in pedestrian injuries among Hispanic children

OBJECTIVES

In an earlier population based surveillance study of pediatric injuries, the rate of Hispanic children injured as pedestrians was 63/100,000 compared with 17/100,000 for non-Hispanic white children. The present study was designed to examine the effect of family, social, and cultural factors on the rate of pedestrian injury in a population of Hispanic children in the southwestern US.

METHODS

A case-control study of pedestrian injuries among Hispanic children. The sample consisted of 98 children 0-14 years of age hospitalized as a result of a pedestrian injury and 144 randomly selected neighborhood controls matched to the case by city, age, gender, and ethnicity. Cases were compared with controls using conditional logistic regression; in the study design the odds ratio (OR) estimates the incidence rate ratio.

RESULTS

The following family and cultural variables were associated with an increased risk of injury: household crowding (OR = 2.8, 95% confidence interval (CI) 1.1 to 7.1 for 1.01-1.5 persons per room, compared with < or = 1.0 persons per room), one or more family moves within the past year (OR 2.2, 95% CI 1.2 to 4.1), poverty (OR 1.9, 95% CI 1.1 to 3.3), and inability of mother (OR 3.6, 95% CI 1.3 to 10) or father (OR 5.6, 95% CI 1.5 to 20) to read well. However, children in single parent households and children whose parents did not drive a car, had less education, or were of rural origin, did not have an increased rate of injury.

CONCLUSIONS

These results have implications for childhood pedestrian prevention efforts for low income, non-English speaking Hispanic populations, and perhaps for other immigrant and high risk groups. Prevention programs and materials need to be not only culturally sensitive but also designed for those with limited reading skills. In addition, environmental interventions that provide more pedestrian friendly neighborhoods must be considered.

Factors associated with restraint use of children in fatal crashes

OBJECTIVE

This study was designed to characterize the restraint use of children in fatal crashes and to determine factors that were related to child restraint use.

METHODS

Crashes in which a vehicle occupant died were selected from the 1994 Fatal Analysis Reporting System data. Restraint use of children (0-9 years) in these crashes was characterized and examined in relation to vehicle and driver characteristics.

RESULTS

Restraint use declined with increasing age of children and increasing number of occupants. Restraint use was also lower in older vehicles, in pickups and large vans, between 3 AM and 6 AM, and in rural areas. Driver characteristics associated with lower restraint use of child passengers included unrestrained drivers, younger drivers, and alcohol use at the time of crash. Driver restraint use was the strongest predictor of child restraint use. Differences in restraint use by age of the child, number of occupants, time, urban/rural area, and driver restraint use persisted in a logistic model.

CONCLUSION

Restraint use in crashes is substantially lower than that in observational studies, suggesting that these studies are not reflective of high-risk conditions for crashes in which children are involved. Child occupant protection counseling must stress restraint use under all conditions of travel. Local, state, and national efforts must be aimed at increasing family occupant protection for the entire family.

Demographic risk factors for injury among Hispanic and non-Hispanic white children: an ecologic analysis

OBJECTIVES

To determine the effects of neighborhood levels of poverty, household crowding, and acculturation on the rate of injury to Hispanic and non-Hispanic white children.

SETTING

Orange County, California.

METHODS

An ecologic study design was used with census block groups as the unit of analysis. Measures of neighborhood poverty, household crowding, and acculturation were specific to each ethnic group. Poisson regression was used to calculate mutually adjusted incidence rate ratios (IRRs) corresponding to a 20% difference in census variables.

RESULTS

Among non-Hispanic white children, injury rates were more closely associated with neighborhood levels of household crowding (adjusted IRR 2.36, 95% confidence interval (CI) 1.22 to 4.57) than with neighborhood poverty (adjusted IRR 1.06, 95% CI 0.89 to 1.26). For Hispanic children, the strongest risk factors were the proportion of Hispanic adults who spoke only some English (compared with the proportion who spoke little or no English, adjusted IRR 1.26, 95% CI 1.04 to 1.53) and the proportion who were US residents for < 5 years (adjusted IRR 1.20, 95% CI 1.001 to 1.43). Neighborhood levels of household crowding were not related to injury among Hispanic children (adjusted IRR 0.98, 95% CI 0.89 to 1.08), but surprisingly, neighborhood poverty was associated with lower injury rates (adjusted IRR 0.89, 95% CI 0.81 to 0.97).

CONCLUSIONS

Cultural and geographic transitions, as well as socioeconomic differences, appear to contribute to differences in childhood injury rates between ethnic groups.

Functional separation of pseudopod extension and particle internalization during Fc gamma receptor-mediated phagocytosis

Receptors for the Fc portion of immunoglobulin (Ig)G (Fc gamma R) mediate phagocytosis of IgG-opsonized particles by a process that can be divided into four major steps: receptor-ligand binding, pseudopod extension, internalization, and lysosomal fusion. We have expressed single classes of Fc gamma R in COS fibroblasts to examine the structural determinants necessary to complete the four steps of phagocytosis. Using phase contrast, fluorescence, confocal, and electron microscopy we have demonstrated that Fc gamma R-expressing COS cells can phagocytose in a manner similar to that of professional phagocytes. We have further analyzed the capacity of the three classes of Fc gamma R to phagocytose, placing special emphasis on the Fc gamma RIA-gamma chain complex, which allowed us to examine independently the roles of the ligand-binding unit (Fc gamma RIA) and the signaling unit (gamma chain). We found that receptor complexes containing a conserved tyrosine activation motif (ITAM), as found in the cytoplasmic domain of Fc gamma RIIA and in the gamma chain associated with Fc gamma RIA and Fc gamma RIIIA, readily internalized target particles. In contrast, Fc gamma RIA alone, having no ITAM, was unable to internalize target particles efficiently, but did mediate pseudopod extension. Cotransfection of gamma chain with Fc gamma RIA restored the ability of the receptor to internalize target particles. A mutant Fc gamma RIA in which the cytoplasmic domain had been deleted was also capable of mediating pseudopod extension, showing that neither the gamma chain nor the cytoplasmic domain of Fc gamma RIA were required for this step. Cytochalasin D, an inhibitor of actin polymerization, blocked particle internalization by all Fc gamma R, but did not block pseudopod extension. Staining the Fc gamma RIA COS cells for F-actin and for tyrosine phosphoproteins, we found that actin did not polymerize during Fc gamma RIA-mediated pseudopod extension, nor were tyrosine kinases activated. Our data suggest that pseudopod extension and internalization are functionally distinct steps mediated through different pathways.

Adult attachment and long-term effects in survivors of incest

OBJECTIVE

The aim of the study was to test the hypothesis that adult attachment is related to distress and personality disorders in incest survivors.

METHOD

Adult female incest survivors recruited from the community participated in a structured interview (Family Attachment Interview; Bartholomew & Horowitz, 1991) and completed measures of current functioning (Impact of Event Scale, SCL-10, Beck Depression Inventory) and personality (MCMI-II). Complete data from 92 cases out of the total sample of 112 were analyzed.

RESULTS

Analyses of variance suggested that attachment (as represented by a category) was significantly related to personality structure, with fearful individuals showing more avoidant, self-defeating, and borderline tendencies and preoccupied individuals showing more dependent, self-defeating, and borderline tendencies than secure or dismissing individuals. Results of hierarchical regression analyses suggested that attachment (as represented by four dimensions) was significantly associated with personality structure, depression and distress, and abuse severity with post traumatic stress disorder (PTSD) symptoms (intrusive thoughts and avoidance of memories) and depression.

CONCLUSIONS

The findings demonstrated the propensity for insecure attachment among incest survivors. Sexual abuse severity and attachment have significant but distinct effects on longterm outcome; abuse characteristics predict classic PTSD symptoms and attachment insecurity predicts distress, depression, and personality disorders above and beyond any effects of abuse severity.

A sublethal dose of LPS to pregnant rats induces TNF-alpha tolerance in their 0-day-old offspring

The newborn has high mortality in septic shock. Induction of endotoxin tolerance may prevent endotoxic shock in the newborn. The present study showed that a small dose of Salmonella enteritidis lipopolysaccharide (S. ent. LPS), Rc mutant Escherichia coli lipopolysaccharide (J5 LPS), or tumor necrosis factor-alpha (TNF-alpha) given to pregnant rats on the 19th day of gestation induced endotoxin tolerance in their 0-day-old offspring. S. ent. LPS or J5 LPS injected into pregnant rats increased plasma endotoxin-like activity in dams, although not in their fetuses, and increased plasma TNF-alpha concentration in both dams and their fetuses. The endotoxin-tolerant newborn rats were also resistant to TNF-alpha. In those newborn rats, an LPS injection increased plasma TNF-alpha concentration and liver TNF-alpha mRNA abundance. These experiments showed that the endotoxin tolerance could be due to TNF-alpha tolerance. In conclusion, prenatal treatment of dams with a small dose of S. ent. LPS, J5 LPS, or TNF-alpha was beneficial in preventing endotoxic shock in the newborn.

Beta2-microglobulin-deficient mice are resistant to bullous pemphigoid

Recent understanding of the mechanism of immunoglobulin G (IgG) catabolism has yielded new insight into antibody-mediated diseases. We proposed that beta2-microglobulin (beta2m)-deficient mice have been protected from systemic lupus erythematosis (SLE)-like syndromes because they lack the beta2m-associated IgG protection receptor (FcRn) and therefore catabolize IgG, including pathogenic IgG autoantibodies, considerably more rapidly than normal mice. Such an hypothesis would predict that beta2m-deficient mice would also be resistant to experimental bullous pemphigoid, a disease with a pathogenesis thought to be much simpler than SLE, being the result of antibody directed toward a pathogenic epitope on the epidermal hemidesmosome that anchors basal keratinocytes to the basement membrane. To test this hypothesis, we administered pathogenic rabbit antibody directed toward the hemidesmosome to beta2m-deficient mice and to normal control mice, both intraperitoneally and intradermally, and assessed the mice clinically, histologically, and immunologically for manifestations of skin disease. We found that the beta2m-deficient mice were protected when the antibody was given intraperitoneally whereas intradermal administration resulted in blisters only slightly less severe than those seen in normal mice. These data would indicate that autoantibody-mediated inflammation might be prevented or controlled by appropriate modulation of FcRn function.

Short-term bladder-wall response to implantation of microstimulators

This study examined the histological response of the bladder wall serosa to the implantation of wireless microstimulators secured with a single polypropylene suture. Two to three microstimulators were implanted in each of three casts for an eight week implantation period to allow sufficient time for a bladder-wall injury-response to develop. Gross observation revealed encapsulation of the microstimulators with no perforation to the bladder lumen or migration from the bladder wall. Histological evaluation confirmed that all the microstimutators were encapsulated with a thin connective tissue sheath and a thickened subserosal layer. There was no remarkable difference in tissue morphology compared with normal bladder wall sections for five of seven stimulators. Two microstimulators in one cat revealed a moderate to severe inflammatory response confined to a small area around the stimulator. In a second cat, a suture extended through the bladder wall. The microstimulators were observed with a scanning electron microscope after explantation. The electrode surfaces, bonding interface between silicon and glass and insulating films that were exposed to biological fluids were carefully inspected. All these observations indicate that the glass capsule reliably protected the sealed cavity of the microstimulators from moisture. These results indicate the microstimulator should be considered for further studies such as effects of stimulation and long-term implantation.

Association of non-receptor protein tyrosine kinases with the Fc gamma RI/gamma-chain complex in monocytic cells

To characterize the functional macromolecular complex of the high affinity receptor for IgG (Fc gamma RI), we have undertaken the identification of the molecules associated with the ligand binding unit and its associated subunit, gamma-chain, in a monocyte cell line, U937. Comparison of the pattern of tyrosine-phosphorylated proteins that coprecipitate with anti-Fc gamma RI or anti-gamma-chain Abs after Fc gamma RI clustering suggests that, like other receptor systems, the different units of the receptor associate or recruit different elements of the signaling pathway. Syk associates preferentially with the gamma-chain subunit and not with Fc gamma RI itself. This association is dependent on receptor clustering and correlates with gamma-chain phosphorylation. The Src kinase Lyn is also part of the receptor complex. Lyn associates with both units of the receptor, and this association is independent of receptor engagement; however, the level of tyrosine phosphorylation of the kinase increases after Fc gamma RI clustering. Association of a 35-kDa phosphoprotein with the binding unit was also observed after receptor clustering. We further found that after Fc gamma RI clustering, tyrosine-phosphorylated Syk associates with Lyn. These data suggest that several levels of interaction occur between these molecules or that different pools of tyrosine kinases become activated after Fc gamma RI clustering.

Association of non-receptor protein tyrosine kinases with the Fc gamma RI/gamma-chain complex in monocytic cells

To characterize the functional macromolecular complex of the high affinity receptor for IgG (Fc gamma RI), we have undertaken the identification of the molecules associated with the ligand binding unit and its associated subunit, gamma-chain, in a monocyte cell line, U937. Comparison of the pattern of tyrosine-phosphorylated proteins that coprecipitate with anti-Fc gamma RI or anti-gamma-chain Abs after Fc gamma RI clustering suggests that, like other receptor systems, the different units of the receptor associate or recruit different elements of the signaling pathway. Syk associates preferentially with the gamma-chain subunit and not with Fc gamma RI itself. This association is dependent on receptor clustering and correlates with gamma-chain phosphorylation. The Src kinase Lyn is also part of the receptor complex. Lyn associates with both units of the receptor, and this association is independent of receptor engagement; however, the level of tyrosine phosphorylation of the kinase increases after Fc gamma RI clustering. Association of a 35-kDa phosphoprotein with the binding unit was also observed after receptor clustering. We further found that after Fc gamma RI clustering, tyrosine-phosphorylated Syk associates with Lyn. These data suggest that several levels of interaction occur between these molecules or that different pools of tyrosine kinases become activated after Fc gamma RI clustering.

The role of the physical and traffic environment in child pedestrian injuries

OBJECTIVE

To identify environmental risk factors on residential streets for pediatric pedestrian injuries.

METHOD

The sample consisted of 39 Latino children 0 to 14 years of age injured as pedestrians on a street in the same block as their home and 62 randomly selected neighborhood control subjects matched to the case by city, age or year of birth, ethnicity, and gender. The cases were identified from a population-based hospital and coroner's office surveillance system established in north-central Orange County, CA. Neighborhood assessments were performed from 3:45 PM to 5 PM, a fairly active time for young pedestrians. The cases were compared with the controls using conditional logistic regressions; in this study design, the odds ratios were interpreted as estimates of the incidence rate ratios.

RESULTS

Children living in a multifamily residence had an incidence of injury greater than that of children living in single-family residence on a single lot (odds ratio [OR] 3.1, 95% confidence interval [CI] 1.3-7.6). The ORs in the highest category were several times those in the lowest category for both parked vehicles (OR 9.6, 95% CI 2.6-36) and total number of pedestrians observed (OR 4.7, 95% CI 1.4-16). Vehicle parking, total pedestrians, vehicular traffic volume, and speed were examined in a multivariate model. The association of vehicles parked on the street with pedestrian injury risk remained significant. Unlike the crude results, progressively greater vehicular speed was associated with a marked increase in risk. Progressively higher vehicular traffic volume was associated with a progressively lower adjusted OR.

CONCLUSION

The results of this analysis would indicate that residential streets with a high proportion of multifamily residence, over 50% of the curb occupied with parked vehicles, and a large number of pedestrians observed in unenclosed areas should receive high priority for intervention programs to reduce pediatric pedestrian injuries. The analysis suggests that on these streets, measures to reduce the amount of street parking (thus increasing visibility) and reductions in vehicular speed should be considered to decrease pedestrian injuries.

The mechanism of platelet aggregation induced by HLA-related antibodies

Immune-mediated platelet activation is emerging as an important pathogenic mechanism of thrombosis. In vitro studies have suggested two distinct pathways for immune-mediated platelet activation; one involving clustering of platelet Fc gamma RIIa, the other involving platelet-associated complement activation. HLA-related antibodies have been shown to cause platelet aggregation, but the mechanism has not been clarified. We evaluated the mechanism of platelet aggregation induced by HLA-related antibodies from nine patients. Antibody to platelet Fc gamma RIIa failed to block platelet aggregation with 8/9 samples, indicating that engagement of platelet Fc gamma RIIa is not necessary for the platelet aggregation induced by HLA-related antibodies. In contrast, platelet aggregation was blocked by antibodies to human C8 (5/7) or C9 (7/7). F(ab')2 fragments of patient IgG failed to induce platelet activation although they bound to HLA antigen on platelets. Intact patient IgG failed to aggregate washed platelets unless aged serum was added. The activating IgG could be adsorbed by incubation with lymphocytes and eluted from the lymphocytes. These results indicate that complement activation is involved in the aggregation response to HLA-related antibodies. This is the first demonstration of complement-mediated platelet aggregation by clinical samples. Five of the patients developed thrombocytopenia in relationship to blood transfusion and two patients developed acute thromboembolic disease, suggesting that these antibodies and the complement-dependent pathway of platelet aggregation may be of clinical significance.

Isolation from human placenta of the IgG transporter, FcRn, and localization to the syncytiotrophoblast: implications for maternal-fetal antibody transport

The IgG transporter responsible for ferrying maternal IgG across the human placenta to fetal circulation has not been identified, although the human homologue of the neonatal rat Fc receptor (FcRn), a heterodimer with pH-dependent IgG affinity, structurally similar to MHC Class I molecules, was recently proposed as a candidate. Affirming this hypothesis, we describe herein the specific copurification from human placenta of 46- and 14-kDa proteins by IgG affinity at acid pH. The larger protein, characterized by its amino acid sequence and by immunoblot, is the alpha-chain of human FcRn (hFcRn). The smaller is beta2-microglobulin. Their coisolation by ligand affinity suggests that they comprise the hFcRn heterodimer. Placenta sections stained immunohistochemically with anti-hFcRn alpha-chain peptide Abs show extensive expression of hFcRn in the syncytiotrophoblast and traces in the endothelium and other unidentified cells of the villus stroma. We find alpha-chain mRNA by Northern analysis in human placenta and in human trophoblast-like cell lines (JEG-3, ED27) but not in a human myelocytic cell line (HL60). We suggest that the placental hFcRn heterodimer may transport IgG to the fetus by a mechanism in which maternal IgG is pinocytosed nonspecifically and then carried to fetal tissues by a pH gradient from acidic endosomes to the pH-neutral basolateral surface of the syncytiotrophoblast. Furthermore, the known characteristics of FcRn suggest a wider function, that it is the receptor postulated by Brambell in the 1960s to regulate tissue and serum IgG concentrations by controlling IgG transport and catabolism.

Isolation from human placenta of the IgG transporter, FcRn, and localization to the syncytiotrophoblast: implications for maternal-fetal antibody transport

The IgG transporter responsible for ferrying maternal IgG across the human placenta to fetal circulation has not been identified, although the human homologue of the neonatal rat Fc receptor (FcRn), a heterodimer with pH-dependent IgG affinity, structurally similar to MHC Class I molecules, was recently proposed as a candidate. Affirming this hypothesis, we describe herein the specific copurification from human placenta of 46- and 14-kDa proteins by IgG affinity at acid pH. The larger protein, characterized by its amino acid sequence and by immunoblot, is the alpha-chain of human FcRn (hFcRn). The smaller is beta2-microglobulin. Their coisolation by ligand affinity suggests that they comprise the hFcRn heterodimer. Placenta sections stained immunohistochemically with anti-hFcRn alpha-chain peptide Abs show extensive expression of hFcRn in the syncytiotrophoblast and traces in the endothelium and other unidentified cells of the villus stroma. We find alpha-chain mRNA by Northern analysis in human placenta and in human trophoblast-like cell lines (JEG-3, ED27) but not in a human myelocytic cell line (HL60). We suggest that the placental hFcRn heterodimer may transport IgG to the fetus by a mechanism in which maternal IgG is pinocytosed nonspecifically and then carried to fetal tissues by a pH gradient from acidic endosomes to the pH-neutral basolateral surface of the syncytiotrophoblast. Furthermore, the known characteristics of FcRn suggest a wider function, that it is the receptor postulated by Brambell in the 1960s to regulate tissue and serum IgG concentrations by controlling IgG transport and catabolism.

Perinatal nutrition enriched with omega-3 polyunsaturated fatty acids attenuates endotoxic shock in newborn rats

Sepsis and septic shock continue to have a high mortality and morbidity in the newborn. Eicosanoids are important mediators in Gram negative septic shock. Omega-3 polyunsaturated fatty acids (omega-3) decrease production of biologically active 2-series eicosanoids. Therefore, we hypothesized that omega-3-enriched diet could decrease 2-series eicosanoids and attenuate endotoxic shock in newborn rats. Sprague-Dawley rat dams were fed with either omega-3 polyunsaturated fatty acid-enriched diet (omega-3 PURA) or omega-6 polyunsaturated fatty acid enriched diet (omega-6PUFA; controls) from the 16th day of gestation until 10 days after parturition. In 10 day old rats, shock was induced by an intraperitoneal injection of Salmonella enteritidis lipopolysaccharide. The omega-3PUFA decreased the mortality of endotoxic shock. In omega-6PUFA, lipopolysaccharide induced hyperglycemia at 2 h and hypoglycemia thereafter without an elevation in plasma insulin concentration, omega-3PUFA attenuated the hyperglycemia and hypoglycemia. omega-3PUFA attenuated the decrease of liver phosphoenolpyruvate ca-boxykinase mRNA abundance, suggesting preserved gluconeogenesis. Therefore, perinatal feeding with omega-3PUFA was beneficial in attenuating glucose dyshomeostasis in newborn rats with endotoxic shock and may be a novel approach to the prevention of endotoxic shock in the newborn.

Monocyte IL-8 release is induced by two independent Fc gamma R- mediated pathways

Cross-linking of PBMC and monocyte Fc gamma R on immobilized IgG stimulates IL-8 release. We used immobilized anti-Fc gamma R Abs to determine which of the three surface Fc gamma R regulated this IL-8 secretion. Fc gamma RIII cross-linking stimulated PBMC to release 5 times more IL-8 than did either Fc gamma RI or Fc gamma RII clustering (p = 0.001) and stimulated 77% more IL-8 release from PBMC than that from purified monocytes (p = 0.001). In contrast, only Fc gamma RI cross-linking significantly induced monocytes to release IL-8 (p = 0.05). Since purified lymphocytes release little IL-8 in response to immobilized IgG or anti-Fc gamma RIII Abs, we hypothesized that lymphocyte Fc gamma R cross-linking augmented monocyte IL-8 release. Supernatants from IgG- or Fc gamma RIII -stimulated lymphocytes induced monocytes to release more IL-8 than lymphocytes incubated on plastic alone (p = 0.002 and p = 0.003, respectively). THP-1 cells, which do not produce IL-8 in response to Fc gamma i]R cross-linking, also released IL-8 in response to supernatants from IgG- or Fc gamma RIII-stimulated lymphocytes, suggesting that the supernatant activity was not soluble immune complexes. The IL-8-stimulating activity was heat labile, suggesting that the activity is a protein. However, we could not reproduce or block this activity using recombinant cytokines or neutralizing anti-cytokine Abs. Thus, monocyte IL-8 is stimulated directly through Fc gamma RI cross-linking and indirectly through an Fc gamma RIII-stimulated soluble lymphocyte factor.

Monocyte IL-8 release is induced by two independent Fc gamma R- mediated pathways

Cross-linking of PBMC and monocyte Fc gamma R on immobilized IgG stimulates IL-8 release. We used immobilized anti-Fc gamma R Abs to determine which of the three surface Fc gamma R regulated this IL-8 secretion. Fc gamma RIII cross-linking stimulated PBMC to release 5 times more IL-8 than did either Fc gamma RI or Fc gamma RII clustering (p = 0.001) and stimulated 77% more IL-8 release from PBMC than that from purified monocytes (p = 0.001). In contrast, only Fc gamma RI cross-linking significantly induced monocytes to release IL-8 (p = 0.05). Since purified lymphocytes release little IL-8 in response to immobilized IgG or anti-Fc gamma RIII Abs, we hypothesized that lymphocyte Fc gamma R cross-linking augmented monocyte IL-8 release. Supernatants from IgG- or Fc gamma RIII -stimulated lymphocytes induced monocytes to release more IL-8 than lymphocytes incubated on plastic alone (p = 0.002 and p = 0.003, respectively). THP-1 cells, which do not produce IL-8 in response to Fc gamma i]R cross-linking, also released IL-8 in response to supernatants from IgG- or Fc gamma RIII-stimulated lymphocytes, suggesting that the supernatant activity was not soluble immune complexes. The IL-8-stimulating activity was heat labile, suggesting that the activity is a protein. However, we could not reproduce or block this activity using recombinant cytokines or neutralizing anti-cytokine Abs. Thus, monocyte IL-8 is stimulated directly through Fc gamma RI cross-linking and indirectly through an Fc gamma RIII-stimulated soluble lymphocyte factor.

Extremely low-birth-weight children and their peers. A comparison of school-age outcomes

OBJECTIVE

To document 7-year developmental and educational outcomes in a cohort of predominantly white, middle-class, extremely low-birth-weight (ELBW, < 1000 g) children to address the incidence of increased developmental disability and the need for special educational services.

DESIGN

Observational study.

PATIENTS

Fifty-four ELBW children and 58 comparison children, who were matched for race, gender, and socio-economic status (30 with low birth weights [1500-2500 g] and 28 with birth weights > 2500 g). The ELBW cohort was drawn from 104 presurfactant survivors born between 1984 and 1986 and cared for in a single hospital.

SETTING

Suburban, university-based tertiary referral center.

MAIN OUTCOME MEASURES

Teachers' reports of classroom placement and special education services and tests of cognitive, motor, language, and visual-motor integration abilities were studied.

RESULTS

Twenty-seven (50%) of 54 ELBW children were in regular classrooms with no special services compared with 21 (70%) of 30 in the low-birth-weight group and 27 (93%) of 28 in the full-term group, indicating a significant trend toward increasing need for special services with decreasing birth weight across the 3 groups (P < .001). The ELBW group scored significantly lower than the comparison groups on all tests, although generally within the average range. Seventy-nine percent of ELBW children had average cognitive scores, but they averaged 14 to 17 points lower than the 2 comparison groups. Twenty percent of the ELBW children had significant disabilities including cerebral palsy, mental retardation, autism, and low intelligence with severe learning problems.

CONCLUSIONS

Even with optimal socioeconomic environments, 20% of ELBW children are significantly disabled, and 1 of every 2 ELBW children requires special educational services. Objective testing pinpointed weakness on all measures compared with matched peer groups.