Loss of B Cells in Patients with Heterozygous Mutations in IKAROS.

BACKGROUND: Common variable immunodeficiency (CVID) is characterized by late-onset hypogammaglobulinemia in the absence of predisposing factors. The genetic cause is unknown in the majority of cases, and less than 10% of patients have a family history of the disease. Most patients have normal numbers of B cells but lack plasma cells. METHODS: We used whole-exome sequencing and array-based comparative genomic hybridization to evaluate a subset of patients with CVID and low B-cell numbers. Mutant proteins were analyzed for DNA binding with the use of an electrophoretic mobility-shift assay (EMSA) and confocal microscopy. Flow cytometry was used to analyze peripheral-blood lymphocytes and bone marrow aspirates. RESULTS: Six different heterozygous mutations in IKZF1, the gene encoding the transcription factor IKAROS, were identified in 29 persons from six families. In two families, the mutation was a de novo event in the proband. All the mutations, four amino acid substitutions, an intragenic deletion, and a 4.7-Mb multigene deletion involved the DNA-binding domain of IKAROS. The proteins bearing missense mutations failed to bind target DNA sequences on EMSA and confocal microscopy; however, they did not inhibit the binding of wild-type IKAROS. Studies in family members showed progressive loss of B cells and serum immunoglobulins. Bone marrow aspirates in two patients had markedly decreased early B-cell precursors, but plasma cells were present. Acute lymphoblastic leukemia developed in 2 of the 29 patients. CONCLUSIONS: Heterozygous mutations in the transcription factor IKAROS caused an autosomal dominant form of CVID that is associated with a striking decrease in B-cell numbers. (Funded by the National Institutes of Health and others.).

Effects of group B streptococci on cord and adult mononuclear cell interleukin-12 and interferon-gamma mRNA accumulation and protein secretion.

Group B streptococci (GBS) are a major cause of early-onset infection in neonates. Neonates, who have defects in neutrophil function that likely contribute to susceptibility to GBS infection, are deficient in the production of the phagocyte activator interferon (IFN)-gamma. GBS-stimulated mRNA accumulation and protein secretion of IFN-gamma and interleukin (IL)-12, a major enhancer of IFN-gamma production, by mixed mononuclear cells (MMCs) from umbilical cord and adult peripheral blood was examined. GBS-exposed cord blood MMCs secreted lower concentrations of both IL-12 and IFN-gamma proteins than did MMCs from adults. IL-12 and IFN-gamma mRNA accumulation was examined by use of comparative reverse transcriptase-polymerase chain reaction. Cord blood MMCs accumulated less mRNA for both IL-12 and IFN-gamma than did adult blood MMC. The deficiency in cord blood cell production of IL-12 may have a role in inadequate IFN-gamma production, which contributes to the unique susceptibility of neonates to GBS infections.

Defective interleukin-12/interferon-gamma pathway in patients with hyperimmunoglobulinemia E syndrome.

OBJECTIVE: Patients with the hyperimmunoglobulinemia E (hyper-IgE) syndrome are reported to have defective production of interferon gamma (IFN-gamma). Because IFN-gamma is a major activator of polymorphonuclear leukocytes (PMNs), this could result in defective PMN chemotaxis and markedly elevated IgE levels because of the unopposed action of interleukin (IL)-4. IL-12, an important enhancer of IFN-gamma production, also suppresses IgE production. This study assessed the IL-12/IFN-gamma pathway in patients with hyper-IgE syndrome. METHODS: Production of IL-12 and IFN-gamma by mononuclear cells from 10 patients with hyper-IgE syndrome in response to a number of stimuli was determined, as well as the effect of IL-12 on IFN-gamma release and cell proliferation. RESULTS: IL-12 and IFN-gamma production by the patients' cells was similar to that of control subjects independent of the stimulus used, except for Staphylococcus aureus, with which cells of patients with hyper-IgE syndrome released markedly less IFN-gamma (19.8%; P <.002). The ability of recombinant IL-12 to enhance IFN-gamma release from patients' cells in response to all stimuli was, however, significantly lower than with control cells (12% to 51%; P <.03). CONCLUSION: The lymphocytes of patients with hyper-IgE syndrome have an impaired response to IL-12, resulting in decreased IFN-gamma production, which may be of key importance in the pathogenesis of the immune abnormalities of hyper-IgE syndrome.

Intracellular and extracellular cytokine production by human mixed mononuclear cells in response to group B streptococci.

Group B streptococci (GBS) are a major cause of severe infection in newborns, pregnant females, and other immunocompromised hosts. Infection often includes septicemia, shock, pneumonia, and respiratory failure. In previous studies, we have reported that GBS induce marked production of tumor necrosis factor alpha (TNF-alpha) by human mononuclear cells. The present study was designed to measure the production of TNF-alpha as well as additional cytokines, including interleukin 1beta (IL-1beta), IL-6, IL-8, IL-12, and gamma interferon (IFN-gamma) but also to determine from what cells and at what time point during incubation with GBS that these cytokines are produced. Mixed mononuclear cells were incubated with heat-killed GBS, media alone, or 1 microg of Escherichia coli lipopolysaccharide (LPS). Brefeldin A was added to each sample prior to staining, which prevented the export of cytokines by the Golgi apparatus. The cells were then stained with the appropriate conjugated antibodies and analyzed by using a flow cytometer. Results indicate that intracellular cytokines appear, in almost all cases, simultaneous to or before secreted proteins are detected. In contrast to the response to LPS, where TNF-alpha, IL-1beta, IL-6, and IL-8 appear almost simultaneously, the human monocyte response to GBS results in the production of TNF-alpha but delayed appearance of IL-1beta, IL-6, and IL-8. The lymphocyte response to GBS was also strikingly different from that to LPS in that both secreted IFN-gamma and IL-12 was detected, while LPS failed to induce production of these critical cytokines. This suggests an important role for TNF-alpha, IFN-gamma, and IL-12 in GBS pathogenesis and/or immunity.

The effect of lactic acid on mononuclear cell secretion of proinflammatory cytokines in response to group B streptococci.

This study found that lactate alone had a stimulatory effect (207.1 +/- 16.3%; P = .001) on tumor necrosis factor (TNF)-alpha production by human mononuclear cells with the most profound secretion being at pathologic concentrations of 4-8 mM lactate. Furthermore, exposure of these mononuclear cells to group B streptococci (GBS, 10(5) cfu) resulted in TNF-alpha production of up to 621.1 +/- 42% of control; the combination of lactic acid and GBS increased TNF-alpha production up to 1019.3 +/- 16.1% (P = .001). The combination of GBS and lactate also enhanced the secretion of interleukin (IL)-1beta and IL-6. Lactate in pathologic concentrations, therefore, likely enhances the secretion of these inflammatory mediators and contributes to septic shock and meningitis caused by GBS.

Regulation of decidual cell chemokine production by group B streptococci and purified bacterial cell wall components.

OBJECTIVE: Our purpose was to determine whether cultured human decidual cells produce chemokines in response to different strains of group B streptococci and purified bacterial cell wall components. STUDY DESIGN: Human decidual cells were cultured from term placentas by standard techniques. Different strains of group B streptococci were isolated from neonates with early-onset group B streptococci sepsis. Confluent cell monolayers were incubated with these different strains of group B streptococci and various concentrations of purified bacterial cell wall components (including lipoteichoic acid, sialic acid, lipopolysaccharide, and lipid A) for 16 hours at 37 degrees C. Culture supernatants were collected and assayed for macrophage inflammatory protein-1 alpha and interleukin-8. Statistical analysis was by analysis of variance. RESULTS: We found that cultured human decidual cells produced significant amounts of the two chemokines macrophage inflammatory protein-1 alpha and interleukin-8 in a strain-specific fashion to the various different strains of group B streptococci tested, from 215% to 421% over baseline production (p < 0.05 by analysis of variance). Also, we found that incubation of decidual cells with various concentrations of lipoteichoic acid, sialic acid, lipopolysaccharide, and lipid A resulted in significant concentration-dependent increases in decidual cell macrophage inflammatory protein-1 alpha and interleukin-8 production (p < 0.05.) CONCLUSIONS: Decidual cells produced significant amounts of the chemokines macrophage inflammatory protein-1 alpha and interleukin-8 in response to intact group B streptococci in a strain-specific fashion and in response to various concentrations of different bacterial cell wall components. Because chemokines are important mediators signaling migration of different immune effector cells into areas of inflammation, we suggest that decidual cell chemokine production in response to bacteria and bacterial cell wall components may be a key early event in the pathogenesis of infection-associated preterm labor.

Serologic evidence for a class I group A streptococcal infection among rheumatic fever patients.

Group A streptococci (GAS) of serotypes most commonly associated with rheumatic fever (RF) outbreaks differ from many other serotypes by the presence of a unique, surface-exposed epitope on the M protein molecule. Based on the presence or absence of this epitope, GAS are categorized as class I or II, respectively. The objective of this study was to determine whether RF patients have an altered immune response to the class I-specific epitope. Immunoreactivity to class I- and class II-specific epitopes was determined for serum IgG derived from persons with a recent history of acute RF, uncomplicated GAS pharyngitis, and no known recent GAS infection. The results indicate that only RF patients display elevated levels of serum IgG directed towards the class I-specific epitope; they lack immunoreactivity to the class II epitope. The serologic findings strongly suggest that many of the RF patients were recently infected with a class I GAS isolate.

Effects of fibronectin and group B streptococci on tumour necrosis factor-alpha production by human culture-derived macrophages.

Group B streptococci (GBS) are an important cause of sepsis and shock in the new-born. We have previously reported that GBS induce the production of tumour necrosis factor-alpha (TNF-alpha) by human monocytes and culture-derived macrophages. We have also shown that fibronectin (FN) promotes interaction between GBS and human phagocytes. In the present study, we investigated the effect of FN and GBS on the production of TNF-alpha by adult and neonatal culture-derived macrophages. We report that soluble FN alone was a strong stimulus for the production of TNF-alpha by culture-derived macrophages (FN 50 micrograms/ml = 623.33 +/- 47 pg/ml TNF, versus media alone 3 +/- 1.5 pg/ml; P < 0.0001). While GBS also induce the production of TNF-alpha by macrophages, the addition of FN to GBS had more than an additive effect on TNF-alpha levels. FN-mediated TNF-alpha production by macrophages was inhibited by both soluble arginine-glycine-aspartic acid (RGD) peptide (71%; P < 0.0001) and anti-beta 3-integrin monoclonal antibody 7G2 (54%; P < 0.0001). Neonatal culture-derived macrophages produced significantly more TNF-alpha in response to GBS (356.4 pg/ml +/- 27.7) than adult cells did (222.0 pg/ml +/- 21.0; P = 0.037), and dramatically more in response to FN alone (neonatal 1931.0 pg/ml +/- 23.0 versus adult 463.5 43.5 pg/ml; P < 0.0001). FN may contribute to the high levels of TNF-alpha production implicated in the pathophysiology of GBS sepsis and shock.

Effects of fibronectin on actin organization and respiratory burst activity in neutrophils, monocytes, and macrophages.

Previous studies have shown that fibronectin (Fn) enhances phagocytosis and killing of antibody-coated bacteria by neutrophils and macrophages. In an attempt to understand the mechanism of this enhancement, we have investigated the effects of Fn on phagocytosis-related actin organization as well as respiratory burst activity in neutrophils, monocytes and culture-derived macrophages. Employing an NBD-phallacidin flow cytometric analysis of filamentous actin formation, we found that Fn promotes rapid actin polymerization within 30 seconds in neutrophils, monocytes, and macrophages, but not lymphocytes. Enhancement of actin polymerization by Fn was concentration-dependent and mediated by a pertussis toxin- but not cholera toxin-sensitive G protein. Inhibition of protein kinase C by sphingosine (20 microM), calcium influx by verapamil (0.1 mM), or intracellular calcium mobilization by 8-(N,N-diethyl-amino) octyl-3,4,5-trimethoxybenzoate HCl (TMB-8; 0.1 mM) did not block Fn-enhanced actin polymerization in phagocytes. Incubation of neutrophils and macrophages on microtiter plates precoated with Fn suppressed superoxide (O2-) production induced by IgG- and IgA- opsonized group B streptococci. In contrast, Fn significantly enhanced IgA- and IgG-mediated O2- production by freshly isolated monocytes. These data suggest that Fn enhances phagocytosis, presumably through G protein-coupled cytoskeleton reorganization and augments O2- production by circulating monocytes. In contrast, it appears to suppress O2- production by the active phagocytic cells, neutrophils and macrophages. This may result in enhanced phagocytosis and intracellular killing of microorganisms without damaging interstitial tissues.

Production of tumor necrosis factor by human cells in vitro and in vivo, induced by group B streptococci.

Tumor necrosis factor alpha (TNF alpha) has been implicated as one of the major mediators of the gram-negative septic shock syndrome. In our studies, group B streptococci (GBS) induced the production of TNF alpha by human mononuclear cells in a dose- and time-dependent manner. Human mixed mononuclear cell cultures exposed to an encapsulated (657.6 +/- 71.3 pg/ml; n = 30 preparations) or an unencapsulated transposon mutant of type III GBS (755.8 +/- 54.7 pg/ml; n = 9) produced similar amounts of TNF alpha. Isolated monocytes and culture-derived macrophages produced higher amounts of TNF alpha (1565 +/- 211 and 1790 +/- 928 pg/ml respectively) in response to GBS than did mixed mononuclear cell cultures. In response to GBS, mixed mononuclear cells from neonates produced significantly more TNF alpha (729.1 +/- 45 vs 520.3 +/- 47.2 pg/ml; p = 0.004) than did cells from adults. Examination of specimens from patients with neonatal GBS disease revealed detectable levels of TNF alpha (7 to 424 pg/ml) in the serum of 5 of 10 patients with sepsis, in 5 of 5 urine samples from infants with sepsis, and in the cerebrospinal fluid of 1 patient with meningitis. These results suggest both a major role for TNF alpha in the pathogenesis of human neonatal GBS sepsis and shock and a potential role for immunotherapy directed against this cytokine in this fulminant neonatal bacterial infection.

Mechanism of fibronectin enhancement of group B streptococcal phagocytosis by human neutrophils and culture-derived macrophages.

In previous studies, we reported that fibronectin (FN) markedly enhances phagocytic uptake of antibody-coated group B streptococci (GBS) by human polymorphonuclear leukocytes. Furthermore, administration of FN along with a GBS type-specific monoclonal or polyclonal antibody to infected neonatal rats significantly enhances survival. In this study, we have examined the molecular mechanism of this enhancement through phagocyte receptors which recognize the Arg-Gly-Asp (RGD) peptide sequences contained within the FN molecule. Incubation of human polymorphonuclear leukocytes or culture-derived macrophages on coverslips coated with GRGDSP but not GRGESP markedly enhanced uptake of immunoglobulin G-coated GBS. The enhancing effect of the RGD-containing peptides was blocked by monoclonal antibodies B6H12 (directed against the integrin-associated protein) and 7G2 (directed against the beta 3-integrin receptor for RGD). These data suggest that FN enhancement of antibody-coated GBS uptake is mediated by the critical RGD sequence. Furthermore, this active peptide sequence may have an important role in immunotherapy of bacterial infections, especially in patients with decreased plasma FN concentrations.

Human recombinant interferon gamma enhances neonatal polymorphonuclear leukocyte activation and movement, and increases free intracellular calcium.

In previous studies, we have reported that after chemotactic factor stimulation, PMNs from neonates fail to undergo certain critical activation steps. Furthermore, the concentration of free intracellular calcium reached is significantly below that of PMNs from adults. Interferon-gamma (IFN-gamma) is a lymphokine that has been shown to activate phagocytic cells, and IFN-gamma messenger RNA production by neonatal mononuclear leukocytes has been reported to be depressed. In the present studies, we found that recombinant human IFN-gamma markedly enhanced the chemotactic responses of PMNs from neonates to levels that were not different from that of PMNs from adults. Furthermore, preincubation of the neonatal cells with this recombinant human lymphokine also corrected the abnormality in intracellular calcium metabolism. These results suggest that this developmental defect in phagocytic cell movement may be the result of an intrinsic defect in IFN-gamma production resulting in deficiency of this critical phagocyte-activating lymphokine.

Effect of fibronectin on IgA-mediated uptake of type III group B streptococci by phagocytes.

Previous studies have shown that a type-specific IgA monoclonal antibody alone or in combination with fibronectin (Fn) enhances protective efficacy in two animal models of group B streptococcal infection. To investigate the mechanisms by which IgA mediates protection, the effects of Fn on phagocytosis of group B streptococci (GBS) opsonized with a type III-specific IgA monoclonal antibody were examined. Specific IgA alone or in combination with Fn did not promote the phagocytosis of GBS by polymorphonuclear leukocytes (PMNL). Fibronectin also had no significant effect on phagocytosis of IgA-opsonized GBS by monocytes. Specific IgA alone promoted phagocytosis of GBS by culture-derived macrophages in a dose-dependent fashion. Fibronectin enhanced macrophage uptake of the GBS opsonized in a suboptimal concentration of specific IgA (phagocytic index = 2.32 +/- 0.56 vs. 3.26 +/- 0.48 with Fn; P less than .05). These data suggest that protection against GBS in neonatal rats by a combination of Fn and specific IgA is mediated by macrophages rather than by PMNL or monocytes. Fibronectin may have a critical role in host defense at sites where IgA and macrophages predominate.

Effect of pentoxifylline on developmental changes in neutrophil cell surface mobility and membrane fluidity.

Polymorphonuclear leukocytes (PMNs) from human neonates respond less efficiently to chemotactic factor stimulation than do PMNs from adults. The biologic mechanisms underlying this developmental process are poorly understood. In previous studies, we have found that pentoxifylline, an agent report to enhance membrane deformability, increased the chemotactic response of neonatal PMNs. In the present studies, we have examined the effect of pentoxifylline on cell surface mobility and membrane fluidity by assessing fluorescent concanavalin A (Con A) capping and fluorescent polarization (FP). Baseline Con A capping was lower in the PMNs of neonates when compared to PMNs from adult controls. Colchicine, which increases capping by disrupting microtubules, exaggerated the differences between the adult and neonatal PMNs. Following exposure of neonatal PMNs to pentoxifylline, colchicine enhanced Con A capping to levels equivalent to those of colchicine-treated PMNs from adults. Employing a fluorescence polarization (FP) assay, we found the fluid state of the membrane of PMNs from neonates was significantly less than that of adult controls. Pentoxifylline alone significantly increased the fluidity of the cell membranes of neonatal PMNs while decreasing elevated basal levels of F-actin in the cell. These data suggest an intrinsic cytoskeletal difference in the PMNs of neonates that may be responsive to pharmacologic manipulation.

Group B streptococci inhibit the chemotactic activity of the fifth component of complement.

Infection with group B streptococci (GBS) is associated with a poor acute inflammatory response in which neutrophils fail to localize at the site of invasion. In the present studies, we have examined the effects of group B streptococci on C-derived chemotactic activity in human serum. Fresh human serum was activated to form C5a and C5adesarg by incubation with zymosan. The activated serum was then incubated with group B organisms, centrifuged, and the supernatants tested for chemotactic activity for human polymorphonuclear leukocytes. Group B organisms caused a dose-dependent decrease in C-dependent chemotactic activity. The degree of inhibition was profound with 1 X 10(9) bacteria/ml (10% of control). Experiments indicated that significant chemotactic factor inactivation occurred within 2 min of exposure to GBS organisms, while maximal inhibition occurred after 30 min incubation. A number of different strains of GBS of types I, II, and III possessed inhibitory activity. In contrast, group D streptococci, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae failed to inhibit the C-derived chemotactic activity in human serum. Group A streptococci that were M protein positive also inactivated C-dependent chemotactic activity in serum, as previously reported. The inhibitory activity of the GBS strains could be abolished by heat or trypsin treatment but not by neuraminidase, pronase, or pepsin. C5a levels in zymosan-activated serum as measured by RIA were not decreased after incubation with an inhibitory strain suggesting that absorption was not involved. SDS-PAGE analysis revealed that group B streptococci degrade the C5a molecule, increasing its electrophoretic mobility by removing a fragment with a m.w. of approximately 650 Da. Thus, one of the reasons for the poor inflammatory response at the site of GBS infection may reside in the ability of these pathogens to inactivate C-derived inflammatory mediators. The GBS C5a-ase activity probably serves as an additional virulence factor for these organisms contributing to the poor inflammatory response characteristic of group B streptococcal infection.

Effects of fibronectin on the interaction of polymorphonuclear leukocytes with unopsonized and antibody-opsonized bacteria.

Fibronectin (Fn) affects the interaction of polymorphonuclear leukocytes (PMNLs) with certain bacteria. Fn alone enhanced the response, in a chemiluminescence (CL) assay, of PMNLs to Staphylococcus aureus (P less than .05) and Staphylococcus epidermidis (P less than .01) but had no effect on type III, group B streptococci (GBS) or Escherichia coli. When GBS or E. coli were first preopsonized in antibody, Fn significantly enhanced the CL response of PMNLs (P less than .05). The intracellular metabolic inhibitor NaN3 but not the extracellular scavengers superoxide dismutase or human serum albumin inhibited Fn-enhanced CL; this fact suggests that enhancement of the respiratory burst by Fn is an intracellular event. We used an acridine orange-crystal violet monolayer assay to examine the effects of Fn on ingestion and intracellular killing of bacteria by PMNLs. Fn alone promoted uptake and killing of S. aureus (P less than .01) and S. epidermidis (P less than .05) by PMNLs but did not enhance monolayer phagocytosis of GBS or E. coli, unless these bacteria were preopsonized in antibody (P less than .01).

Effect of disodium cromoglycate on neutrophil movement and intracellular calcium mobilization.

Disodium cromoglycate (DSCG) is a widely used drug in the treatment of allergy and asthma. Although its mode of action is not completely understood, it appears to prevent activation and release of mediators from mast cells. Neutrophils may also play a prominent role in clinical asthma and in other diseases of the airways. We have therefore studied the effect of DSCG on the activation of neutrophils from healthy adults. DSCG in concentrations of 1, 10, and 50 micrograms/ml significantly inhibited chemotaxis to zymosan-activated serum or formyl-methionyl-leucyl-phenylalanine. When leukotriene B4 was used as the chemoattractant, no inhibition was found. Incubation of the cells with the drug for 30 minutes elicited the most pronounced inhibition. Since calcium is a key factor in the activation of cells, we used the calcium-specific probe Quin-2 to examine free levels of this cation after chemotactic-factor stimulation. Treatment of neutrophils with DSCG significantly reduced intracellular free calcium levels induced by zymosan-activated serum but not leukotriene B4. Thus, it appears that DSCG may function not only to stabilize mast cells in allergy and clinical asthma but also may interfere with neutrophil activation and movement into the airways.

Correction of a developmental defect in neutrophil activation and movement.

In order to more fully understand the mechanisms involved in the developmental defect in polymorphonuclear leukocyte (PMN) movement in human neonates, the authors have examined several events in the activation response sequence. Chemotactic factor receptor numbers have been found to be normal on the PMNs of neonates, but chemotactic factor-induced changes in membrane potential and cyclic adenosine monophosphate concentrations were markedly decreased to absent in the neonatal cells. Because the neonatal PMN lacks the ability to deform normally, we examined the effects of a methylxanthine derivative, pentoxifylline, on the responses of neonatal cells. This agent has been reported to increase cell deformability and improve cell movement. Pentoxifylline had an effect in improving chemotactic function in the PMNs of neonates, while correcting the abnormality in membrane potential. In addition, this agent was found to enhance the movement of cell surface concanavalin A receptors after colchicine treatment. These results suggest that this developmental defect in cell activation and movement may be an abnormality that can be corrected pharmacologically.

Effect of group B streptococcal type-specific antigen on polymorphonuclear leukocyte function and polymorphonuclear leukocyte-endothelial cell interaction.

Neonatal group B streptococcal pneumonia is a severe disease, often resulting in death. Autopsy findings resemble those of hyaline membrane disease. Numerous organisms may be seen in the alveoli, but few polymorphonuclear leukocytes (PMNs) are found in the areas of bacterial invasion. Aggregated PMNs are often found, however, in the pulmonary capillaries. This study was designed to explore the effect of the group B streptococcal (GBS) type III antigen on PMN chemotaxis and PMN-endothelial cell interactions. Human PMNs were isolated and pretreated with 0.25 to 4 micrograms/ml of GBS type III antigen prior to determining their chemotactic response to the chemoattractants formyl-methionyl-leucyl-phenylalanine, zymosan-activated serum, platelet-activating factor, and leukotriene B4. The GBS antigen caused a concentration-dependent inhibition of formyl-methionyl-leucyl-phenylalanine, zymosan-activated serum, and platelet-activating factor-mediated chemotaxis (% inhibition of 38.1 +/- 4.0, 55.5 +/- 3.3, 46.7 +/- 9.7%, respectively; p less than 0.01). Leukotriene B4-mediated chemotaxis was not significantly depressed (21.2% +/- 7.7 inhibition; NSD). Group B streptococcal antigen also inhibited formyl-methionyl-leucyl-phenylalanine-induced PMN adherence to endothelial cells in a concentration-dependent fashion when incubations were performed in the absence of serum. In contrast, incubation of GBS type III antigen with serum deficient in antibody to GBS resulted in a marked enhancement of PMN attachment to human endothelial cells. No significant enhancement of adherence was sen with the antigen in the presence of serum containing GBS type III antibody. These data suggest that the GBS type III antigen by itself may inhibit the influx of PMNs into the local site of infection in the alveoli.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormality in actin polymerization associated with defective chemotaxis in neutrophils from neonates.

In an attempt to determine the mechanism of the profound defect in chemotaxis observed in the neutrophils of human neonates, we have examined the generation of polymerized or filamentous actin (F actin) following stimulation of the cells with chemotactic factors. We have also examined the changes in the intracellular levels of free calcium in neonatal neutrophils and compared the results with those in adult neutrophils. Following exposure to formyl-methionyl-leucyl-phenylalanine (FMLP) or zymosan-activated serum (ZyAS), neutrophils from adult donors showed an increase in intracellular free calcium, as determined by Quin 2/AM fluorescence, and in actin polymerization (45-55%), as measured by nitrobenzoxadiazole phallicidin fluorescence. These responses were abolished by preincubation with the calcium antagonist verapamil (0.1 mM), which inhibits both calcium influx and release from intracellular stores. In marked contrast to the results obtained with neutrophils from adults, neutrophils from newborn infants, which have defective chemotactic responses, failed to generate F actin following FMLP or ZyAS stimulation and developed significantly lower levels of free intracellular calcium.