B cells establish, but do not maintain, long-lived murine anti-peanut IgE(a)

BACKGROUND

Peanut allergy (PNA) has been reported to be transferred to tolerant recipients through organ and bone marrow (BM) transplantation. The roles T and B cells play in establishing, and the roles B cell subsets play in maintaining lifelong anti-peanut IgE levels are unknown.

OBJECTIVES

To determine the cellular requirements for the transfer of murine PNA and to determine the role CD20(+) cells play in maintaining long-lived anti-peanut IgE levels.

METHODS

We developed a novel adoptive transfer model to investigate the cellular requirements for transferring murine PNA. We also treated peanut-allergic (PA) mice with anti-CD20 antibody and measured IgE levels throughout treatment.

RESULTS

Purified B220(+) cells from PA splenocytes and purified CD4(+) cells from naïve (NA) splenocytes are the minimal requirements for the adoptive transfer of PNA. Prolonged treatment of allergic mice with anti-CD20 antibody results in significant depletion of B cell subsets but does not affect anti-peanut IgE levels, symptoms, or numbers of IgE antibody secreting cells (ASCs) in the BM. Adoptive transfer of BM and spleen cells from allergic donors treated with anti-CD20 antibody does not result in the transfer of PNA in NA recipients, demonstrating that anti-CD20 antibody treatment depletes B cells capable of differentiating into peanut-specific IgE ASCs.

CONCLUSIONS AND CLINICAL RELEVANCE

Peanut allergy can be established in a NA hosts with B220(+) cells from PA donors and CD4(+) cells from peanut-NA donors. However, long-term depletion of B220(+) cells with anti-CD20 antibody does not affect anti-peanut IgE levels. These results highlight a novel role for B cells in the development of PNA and provide evidence that long-lived anti-peanut IgE levels may be maintained by long-lived ASCs.

Epitope analysis of Ara h 2 and Ara h 6: characteristic patterns of IgE-binding fingerprints among individuals with similar clinical histories

BACKGROUND

Ara h 2 and Ara h 6 are moderately homologous and highly potent peanut allergens.

OBJECTIVE

To identify IgE-binding linear epitopes of Ara h 6, compare them to those of Ara h 2, and to stratify binding based on clinical histories.

METHODS

Thirty highly peanut-allergic subjects were stratified by clinical history. Sera were diluted to contain the same amount of anti-peanut IgE. IgE binding to overlapping 20-mer peptides of Ara h 2 and Ara h 6 was assessed using microarrays.

RESULTS

Each subject had a unique IgE-binding fingerprint to peptides; these data were coalesced into epitope binding. IgE from subjects with a history of more severe reactions (n = 19) had a smaller frequency of binding events (BEs) for both Ara h 2 (52 BEs of 152 (19X8epitopes) possible BEs and Ara h 6 (13 BEs of 133 (19X7 epitopes) possible BEs) compared to IgE from those with milder histories (n = 11) (Ara h 2: 47 BEs of 88 (11X8 epitopes) possible BEs, P < 0.01; Ara h 6: 25 BEs of 77 (11X7 epitopes) possible BEs, P < 0.001). Using an unsupervised hierarchal cluster analysis, subjects with similar histories tended to cluster. We have tentatively identified a high-risk pattern of binding to peptides of Ara h 2 and Ara h 6, predominantly in subjects with a history of more severe reactions (OR = 12.6; 95% CI: 2.0-79.5; P < 0.01).

CONCLUSIONS AND CLINICAL RELEVANCE

IgE from patients with more severe clinical histories recognize fewer linear epitopes of Ara h 2 and Ara h 6 than do subjects with milder reactions and bind these epitopes in characteristic patterns. Close examination of IgE binding to epitopes of Ara h 2 and Ara h 6 may have prognostic value.

Vitamin E, γ-tocopherol, diminishes ex vivo basophil response to dust mite allergen

Epidemiologic studies suggest that dietary vitamin E is a candidate intervention for atopic disease. We used in vitro and ex vivo exposures to test the hypothesis that the most common dietary isoform of vitamin E, γ-tocopherol (γT), could suppress FcεRI-mediated basophil activation. Rat basophilic leukemia (RBL)-SX38 cells that express human FcεRI were treated with or without γT, followed by stimulation with α-IgE. In the ex vivo study, 20 Der f 1-allergic volunteers consumed a γT-enriched supplement for 7 days. Their basophils were challenged ex vivo with α-IgE and graded doses of Der f 1 before and after the supplementation period. γt treatment of RBL-SX38 cells significantly reduced basophil degranulation and de novo TH2 cytokine production. Daily consumption of a γT-rich supplement by dust mite-allergic volunteers reduced basophil activation after ex vivo dust mite challenge. Vitamin E supplements rich in γT may be useful adjuncts in decreasing atopic disease.

The 2S albumin allergens of Arachis hypogaea, Ara h 2 and Ara h 6, are the major elicitors of anaphylaxis and can effectively desensitize peanut-allergic mice

BACKGROUND

Ara h 2 and Ara h 6, co-purified together in a 13-25 kD fraction (Ara h 2/6; 20 kD fraction) on gel filtration chromatography, account for the majority of effector activity in a crude peanut extract (CPE) when assayed with RBL SX-38 cells sensitized with IgE from human peanut allergic sera.

OBJECTIVES

To determine if Ara h 2/6 are the primary peanut allergens responsible for allergic reactions in vivo and to determine if Ara h 2/6 would be sufficient to prevent allergic reactions to a complete CPE.

METHODS

An oral sensitization mouse model of peanut allergy was used to assess the activity of Ara h 2/6 (20 kD) and CPE without the 20 kD fraction (CPE w/o 20 kD) for allergic provocation challenge and immunotherapy. The activity of these preparations was also tested in an assay of histamine release from human basophils in whole blood.

RESULTS

Compared with mice challenged with control CPE, mice challenged with CPE w/o 20 kD experienced reduced symptoms (P < 0.05) and a smaller decrease in body temperature (P < 0.01). Results with the basophil histamine release assay corroborated these findings (P < 0.01). The mouse model was also used to administer Ara h 2/6 (20 kD) in an immunotherapy protocol, in which peanut-allergic mice treated with the 20 kD fraction experienced significantly reduced symptoms, changes in body temperature, and mast cell protease (MMCP-1) release compared with placebo (P < 0.01 for all parameters). Importantly, immunotherapy with the 20 kD fraction was just as effective as treatment with CPE, whereas CPE w/o 20 kD was significantly less effective for higher dose peanut challenges.

CONCLUSIONS AND CLINICAL RELEVANCE

Ara h 2/6 are the most potent peanut allergens in vivo and can be used to desensitize peanut-allergic mice. These results have potential implications for clinical research in the areas of diagnosis and immunotherapy for peanut allergy.

Effector activity of peanut allergens: a critical role for Ara h 2, Ara h 6, and their variants

RATIONALE

An important property of allergens is their ability to cross-link IgE and activate mast cells and basophils. The effector activity of peanut allergens has not been well characterized.

METHODS

Crude extracts of fresh peanut flour were fractionated by gel filtration. Effector function was assayed by measuring degranulation of RBL SX-38 cells sensitized with IgE from individual sera and from pools of sera of peanut-allergic donors.

RESULTS

Following gel filtration, 75 +/- 7% of the applied protein and 76 +/- 16% (n=3) of the applied activity (assayed with a pool of 11 sera) were recovered in the resultant fractions. The majority (85 +/- 2%; n=3) of the recovered activity resided in a fraction with a theoretical average molecular weight of approximately 20 kDa and a range of 13-25 kDa. When all the individual fractions were recombined, the measured activity was similar to that of the original extract [140 +/- 43% when measured with a pool of serum (n=2) and 66 +/- 7% when measured with individual sera (n=4)]; when all individual fractions excluding the 20 kDa fraction were recombined, the measured activity was only 8 +/- 2% (n=2) of the original extract when assayed with the serum pool and 10 +/- 4% (n=3) when assayed with the individual sera. Two-dimensional gel electrophoresis of this biologically active fraction revealed >60 protein spots. Analysis of 50 of the most prominent spots by matrix-assisted laser-desorption ionization time-of-flight mass spectrometry and of the full mixture by automated tandem mass spectrometry coupled to online capillary liquid chromatography revealed that >97% of the protein mass consisted of Ara h 2.0101, Ara h 2.0201, Ara h 6 isoforms, and variants of these proteins.

CONCLUSIONS

Ara h 2 and Ara h 6 account for the majority of the effector activity found in a crude peanut extract.

Measuring degranulation of mast cells

This unit describes methods for measuring exocytosis of preformed mediators from secretory granules as an indication of IgE receptor-mediated activation of mast cells. The first basic protocol describes the measurement of biogenic amines (serotonin and histamine) secreted by activated rodent mast cells (for serotonin) or rodent and human mast cells (for histamine). The second basic and alternate protocols detail techniques for measuring the release of beta-glucuronidase, an enzyme that is synthesized by human and rodent mast cells, stored in secretory granules, and released during degranulation. Methods for assaying other enzymes released during degranulation, such as beta-hexosaminidase and tryptase, are discussed in the . These protocols can also be applied to basophils where appropriate.

Contribution of Ara h 2 to peanut-specific, immunoglobulin E-mediated, cell activation

BACKGROUND

Ara h 2 is a potent peanut allergen but its contribution to the ability of a crude peanut extract (CPE) to cross-link IgE and activate mast cells has not been rigorously evaluated.

OBJECTIVE

To measure the contribution that Ara h 2 makes to the effector function of a CPE.

METHODS

Ara h 2 was specifically removed from a CPE as demonstrated by immunoblots, 2D gels, and an inhibitory ELISA. Functional assays of sham-treated and Ara h 2-depleted CPEs were performed with RBL SX-38 cells sensitized with IgE from highly peanut-allergic subjects and with naturally sensitized basophils.

RESULTS

Depletion of approximately 99% of the Ara h 2 from the CPE led to an increase in the concentration of the CPE necessary to give 50% of maximal degranulation (EC50) of the SX-38 cells following sensitization with sera that contain anti-Ara h 2 IgE. Assays with a pool of 10 sera showed a small but significant increase in the EC50 following depletion of Ara h 2 (1.65+/-0.15-fold; P<0.05) and assays of seven individual sera showed a similar increase in the average EC50 (1.7+/-0.2-fold; P<0.02). The percent of the anti-peanut IgE that binds Ara h 2 correlated with an increase in the EC50 of the CPE following depletion of Ara h 2 (r=0.83; P<0.02). On the other hand, data from three of these patients studied with a basophil histamine release assay did not show a significant effect of depletion of Ara h 2.

CONCLUSION

Based on its ability to cross-link IgE effectively, Ara h 2 is clearly an important peanut allergen. Its ability to cross-link IgE effectively from a specific serum is related to the proportion of anti-Ara h 2 in that serum but Ara h 2 does not account for a majority of the effector activity of the CPE for any of the sera studied.

In vitro activity of MEKK2 and MEKK3 in detergents is a function of a valine to serine difference in the catalytic domain

MEKK2 and MEKK3 are mitogen-activated protein kinase kinase kinases (MAP3 kinases) of 70 and 71 kDa respectively that are markedly homologous (94%) in their kinase domains. Both MEKK2 and MEKK3 are able to activate the Jun kinase pathway in vivo. However, following routine immunoprecipitation in Triton X-100, MEKK2 but not MEKK3 is able to effectively phosphorylate both SEK-1 and MEK-1 and to undergo autophosphorylation. Unexpectedly, both MEKK2 and MEKK3 are functional in an in vitro kinase assay when cells are solubilized with the closely related detergent, NP-40. Given the high homology between these kinases, we set out to relate this differential sensitivity to Triton X-100 to differences in primary structure. A set of chimeric molecules were generated and the loss of activity in Triton X-100 mapped to kinase domain II/III and specifically to serine 390 of MEKK3 and valine 384 of MEKK2, residues immediately N-terminal to the active site lysine. Mutation of serine 390 of MEKK3 to a valine (as is found in MEKK2) conferred catalytic activity to MEKK3 in Triton X-100 whereas the reciprocal alteration of valine 384 of MEKK2 to a serine conferred lack of activity in Triton X-100 to MEKK2. Search of the protein database identified only three kinases, MEKK3, Pbs2p and Dd-PKI, with a serine or threonine at this site. The presence of a serine or threonine adjacent to the active site lysine in protein kinases is rare and, in MEKK3, results in detergent instability.

Isoforms of Jun kinase are differentially expressed and activated in human monocyte/macrophage (THP-1) cells

Ten isoforms of c-jun N-terminal kinase (JNK) have been described that arise by differential mRNA splicing of three genes. In that the relative expression and function of these different JNK proteins in human monocytic cells is not known, we have examined the JNK isoforms in THP-1 monocyte/macrophage cells. Differentiation of THP-1 cells by exposure to 10(-8) M PMA for 42-48 h enhances cellular responses to LPS, including enhanced activation of total JNK activity and increased phosphorylation of p54 JNK as well as p46 JNK. Examination of JNK proteins on Western blots reveals a predominance of p46 JNK1 and p54 JNK2 proteins. Clearing of lysates by immunoprecipitation of JNK1(99% effective) removes 46% of the JNK enzymatic activity (p < 0.01), whereas clearing of JNK1 plus JNK2 (70% effective) depletes the sample of 72% of the JNK activity (p < 0.01). Further analysis, undertaken with real-time RT-PCR, revealed that 98% of the JNK messages code for three isoforms: JNK1beta1, JNK2alpha1, and JNK2alpha2. The p54 JNK that is phosphorylated in LPS-stimulated, PMA-differentiated THP-1 cells is most likely JNK2alpha2 because 97% of the p54 JNK-encoding messages code for JNK2alpha2. By analogous reasoning, the p46 JNKs that are not heavily phosphorylated, but account for approximately half of the N-terminal c-jun kinase enzymatic activity, are most likely either JNK1beta1 or JNK2alpha1 because they account for 98% of the messages that can code for 46kDa JNKS:

A diabetogenic gene prevents T cells from receiving costimulatory signals

T cell fate following antigen encounter is determined by several intracellular signals generated by the interaction of the T cell with an antigen-presenting cell. In the periphery activation requires T cell receptor signaling (signal one) in combination with costimulatory signals (signal two), usually provided through the cognate interaction of CD28 and B7 molecules. Provision of signal one alone to purified murine peripheral T cells in vitro induces apoptosis or anergy rather than promoting activation. These T cells can be rescued from apoptosis if they are provided with costimulation supplied, for example, by engaging the CD28 co-receptor with an anti-CD28 monoclonal antibody or by adding an exogenous source of interleukin-2. However, a majority of peripheral T cells from autoimmune, diabetes-prone Biobreeding (BB) rats exhibited different responses to these stimuli. T cells from these rats could not be rescued from apoptosis by costimulation. This was not due to the inability of BB-DP T cells to upregulate CD28 and the IL-2 receptor in response to TCR crosslinking. The failure of these costimulatory interactions to rescue BB-DP T cells segregated with the diabetes-susceptibility gene iddm1. Iddm1 in the rat causes peripheral T cell lymphopenia, which is associated with a dramatically shortened peripheral T cell life span. Our results indicate that a diabetogenic gene may contribute to autoimmunity by negating costimulatory signals important for the survival of long-lived peripheral T cells.

Production of TNF-alpha by murine bone marrow derived mast cells activated by the bacterial fimbrial protein, FimH

Production of tumor necrosis factor alpha (TNF-alpha) by mast cells is an important aspect of host defense against gram negative bacteria. In order to define the intracellular pathways utilized by mast cells in this physiological, protective role, we have studied the production of TNF-alpha in bone marrow derived mast cells from the C3H/HeJ (LPS-insensitive) strain following exposure to bacteria expressing the fimbrial protein, FimH. Mast cells exposed to FimH produce TNF-alpha (300-1200 pg/10(6) cells) over 1-3 h compared with 1800-15,000 pg/10(6) cells produced by cells triggered via IgE/antigen. This low level of TNF-alpha production in vitro is compatible with the protective in vivo role of mast cells to produce modest amounts of TNF-alpha in contrast to the large amounts of mediators released during maximal activation. A second difference between the two signals is sensitivity to cyclosporin A (CsA). The IgE/antigen pathway is inhibited by 90-95% at 0.02 to 0.5 microM cyclosporin A whereas the FimH pathway is inhibited by only 40%. These data demonstrate that the intracellular pathway activated by FimH is different from that activated by IgE/antigen both in terms of amount of TNF-alpha produced and in sensitivity to CsA. This is the first evidence that FimH activates mast cells via a pathway that is distinct from that used by IgE/antigen.

Arachidonate-induced eicosanoid synthesis in RBL-2H3 cells: stimulation with antigen or A23187 induces prolonged activation of 5-lipoxygenase

We studied the ability of rat basophilic leukemia (RBL-2H3) cells stimulated with either IgE/antigen or calcium ionophore, A23187, to synthesize LTC4 and PGD2 after addition of exogenous arachidonic acid. RBL-2H3 cells preferentially synthesized PGD2 in response to stimulation with low concentrations of antigen or A23187 while higher concentrations also resulted in a marked synthesis of LTC4. The synthesis of LTC4 was dependent upon initial activation of 5-lipoxygenase by IgE/antigen or A23187, since arachidonic acid lone failed to induce LTC4 synthesis. Following the addition of IgE/antigen or A23187 alone, the synthesis of PGD2 and LTC4 was essentially complete by 10 min. To determine whether a limitation of substrate precluded further eicosanoid synthesis, exogenous arachidonic acid was added to washed cells 15-145 min following the initial stimulation with IgE/antigen or A23187, PGD2 and LTC4 synthesis was resumed following the addition of arachidonic acid to washed prestimulated cells, demonstrating that the termination of eicosanoid synthesis in RBL-2H3 cells was nor caused by the inactivation of cyclooxygenase and 5-lipoxygenase. DNP-lysine was added to cells previously stimulated with IgE/antigen to stop receptor aggregation and this greatly inhibited subsequent production of LTC4 following the addition of arachidonic acid, suggesting that ongoing stimulation of Fc epsilon XsRI was required for LTC4 synthesis in this setting. These results indicate that the magnitude of a physiologic stimulus (IgE/antigen) can profoundly affect the arachidonate metabolites produced by mast cells and that the synthesis of these metabolites quickly becomes limited by substrate availability rather than the activity of cyclooxygenase or 5-lipoxygenase.

High-affinity oligonucleotide ligands to human IgE inhibit binding to Fc epsilon receptor I

Using the systematic evolution of ligands by exponential enrichment (SELEX) method, we have identified oligonucleotides that bind to human IgE with high affinities and high specificity. These ligands were isolated from three pools of oligonucleotides, each representing 10(15) molecules: two pools contained 2'-NH2 pyrimidine-modified RNA with either 40 or 60 randomized sequence positions, and the third pool contained ssDNA with 40 randomized sequence positions. Based on sequence and structure similarities, these oligonucleotide IgE ligands were grouped into three families: 2'-NH2 RNA group A ligands are represented by the 35-nucleotide truncate IGEL1.2 (Kd = 30 nM); 2'-NH2 RNA group B ligands by the 25-nucleotide truncate IGEL2.2 (Kd = 35 nM); and the ssDNA group ligands by the 37-nucleotide truncate DI 7.4 (Kd = 10nM). Secondary structure analysis suggests G quartets for the 2'-NH2 RNA ligands, whereas the ssDNA ligands appear to form stem-loop structures. Using rat basophilic leukemia cells transfected with the human high-affinity IgE receptor Fc epsilon RI, we demonstrate that ligands IGEL1.2 and D17.4 competitively inhibit the interaction of human IgE with Fc1 epsilon RI. Furthermore, this inhibition is sufficient to dose-dependently block IgE-mediated serotonin release from cells triggered with IgE-specific Ag or anti-IgE Abs. Therefore, these oligonucleotide ligands represent a novel class of IgE inhibitors that may prove useful in the fight against allergic diseases.

High-affinity oligonucleotide ligands to human IgE inhibit binding to Fc epsilon receptor I

Using the systematic evolution of ligands by exponential enrichment (SELEX) method, we have identified oligonucleotides that bind to human IgE with high affinities and high specificity. These ligands were isolated from three pools of oligonucleotides, each representing 10(15) molecules: two pools contained 2'-NH2 pyrimidine-modified RNA with either 40 or 60 randomized sequence positions, and the third pool contained ssDNA with 40 randomized sequence positions. Based on sequence and structure similarities, these oligonucleotide IgE ligands were grouped into three families: 2'-NH2 RNA group A ligands are represented by the 35-nucleotide truncate IGEL1.2 (Kd = 30 nM); 2'-NH2 RNA group B ligands by the 25-nucleotide truncate IGEL2.2 (Kd = 35 nM); and the ssDNA group ligands by the 37-nucleotide truncate DI 7.4 (Kd = 10nM). Secondary structure analysis suggests G quartets for the 2'-NH2 RNA ligands, whereas the ssDNA ligands appear to form stem-loop structures. Using rat basophilic leukemia cells transfected with the human high-affinity IgE receptor Fc epsilon RI, we demonstrate that ligands IGEL1.2 and D17.4 competitively inhibit the interaction of human IgE with Fc1 epsilon RI. Furthermore, this inhibition is sufficient to dose-dependently block IgE-mediated serotonin release from cells triggered with IgE-specific Ag or anti-IgE Abs. Therefore, these oligonucleotide ligands represent a novel class of IgE inhibitors that may prove useful in the fight against allergic diseases.

ATP-dependent activation of phospholipase C by antigen, NECA, Na3VO4, and GTP-gamma-S in permeabilized RBL cell ghosts: differential augmentation by ATP, phosphoenolpyruvate and phosphocreatine

Ghosts prepared from rat basophilic leukemia cells (RBL cell ghosts) and permeabilized with alpha-toxin from S. aureus are a simplified system for the study of Fc epsilon RI-mediated activation of phospholipase C (PLC). This activity is dependent upon ATP and magnesium, and is enhanced by the addition of another compound containing an energetic phosphate group, either phosphoenolpyruvate (PEP) or phosphocreatine (PCr). This effect appears to be specific for PEP and PCr in that other compounds with energetic phosphate bonds including fructose 1,6-bisphosphate and additional ATP are not effective. On the contrary, GTP-gamma-S, an activator of G proteins, activates PLC in the presence of ATP alone and this is not further enhanced by the addition of PEP. In addition to Fc epsilon RI and GTP-gamma-S, two other stimuli lead to enhanced activity of PLC in permeabilized RBL cell ghosts: 1) an inhibitor of tyrosine phosphatases (Na3VO4) and 2) an analog of adenosine (NECA). Data presented here extend previous results to show that activation of PLC by GTP-gamma-S is not enhanced either by the addition of PCr or by the addition of a more MgATP. Further new findings include the observations that activation of PLC by Na3VO4 is augmented by PEP and PCr in a fashion similar to that observed for Fc epsilon RI-mediated activation of PLC and that activation of PLC by NECA shows even more marked dependency on PEP than does activation by Fc epsilon RI or Na3VO4.(ABSTRACT TRUNCATED AT 250 WORDS)

A method to trap IgG antibodies within functional membrane vesicles

Monoclonal antibodies have been used extensively to study the roles of specific extracellular proteins in cellular activation. Due to the large size of these molecules, their use for the study of receptor-mediated activation of intracellular processes has been limited. This report describes a method to introduce whole IgG antibody molecules into large functional membrane vesicles (ghosts) derived from rat basophilic leukemia (RBL) cells. Furthermore, an IgG1 mouse monoclonal antibody (JRK) directed against the cytoplasmic portion of the beta subunit of the high affinity receptor for IgE (Fc epsilon RI) can partially inhibit Fc epsilon RI-mediated PI hydrolysis through modest effects on both basal and receptor-mediated activation of phospholipase C.

Phosphoenolpyruvate and creatine phosphate augment ATP and magnesium-dependent, Fc epsilon RI-mediated activation of phospholipase C in RBL cell ghosts

We have previously reported that Fc epsilon RI-mediated activation of PLC occurs in plasma membrane vesicles derived from RBL cells. This activity is dependent on ATP and magnesium, and is greatly enhanced by the addition of either PEP or CP. We undertook these studies to determine whether these compounds augment Fc epsilon RI-mediated activation of PLC because of their ability to form ATP. The specific findings were 1) the addition of increasing amounts of ATP to the ghost vesicles cannot substitute for the combination of ATP and either PEP or CP; 2) the addition of increasing amounts of ATP or a combination of ATP and either PEP or CP results in similar levels of intravesicular ATP; 3) many metabolically related compounds have some activity to support receptor-mediated PI hydrolysis, but only PEP, CP, and 3-PG give a maximal signal; and 4) the inability of ATP alone to support optimal receptor-mediated PI hydrolysis does not appear to be due to the accumulation of ADP is only modestly inhibitory. Taken together, these data are evidence that augmentation of Fc epsilon RI-mediated PI hydrolysis by PEP and CP is not explained simply by the ability of these compounds to generate intravesicular ATP.

Phosphoenolpyruvate and creatine phosphate augment ATP and magnesium-dependent, Fc epsilon RI-mediated activation of phospholipase C in RBL cell ghosts

We have previously reported that Fc epsilon RI-mediated activation of PLC occurs in plasma membrane vesicles derived from RBL cells. This activity is dependent on ATP and magnesium, and is greatly enhanced by the addition of either PEP or CP. We undertook these studies to determine whether these compounds augment Fc epsilon RI-mediated activation of PLC because of their ability to form ATP. The specific findings were 1) the addition of increasing amounts of ATP to the ghost vesicles cannot substitute for the combination of ATP and either PEP or CP; 2) the addition of increasing amounts of ATP or a combination of ATP and either PEP or CP results in similar levels of intravesicular ATP; 3) many metabolically related compounds have some activity to support receptor-mediated PI hydrolysis, but only PEP, CP, and 3-PG give a maximal signal; and 4) the inability of ATP alone to support optimal receptor-mediated PI hydrolysis does not appear to be due to the accumulation of ADP is only modestly inhibitory. Taken together, these data are evidence that augmentation of Fc epsilon RI-mediated PI hydrolysis by PEP and CP is not explained simply by the ability of these compounds to generate intravesicular ATP.

Fc epsilon RI-mediated expression of mRNA for c-fos in rat basophilic leukemia cells does not require ongoing aggregation of the receptor

Cross-linkage of the high-affinity receptor for IgE (Fc epsilon RI) by a polyvalent ligand, leads to activation of mast cells and basophils. We have studied Fc epsilon RI-mediated expression of RNA coding for the protooncogene, c-fos, in rat basophilic leukemia (RBL) cells and specifically have examined the requirements for ongoing receptor aggregation in the generation of this signal. RBL cells were sensitized with IgE specific for 2,4-dinitrophenyl (DNP) and incubated at 37 degrees C in the presence of DNP24BSA or BSA alone. Following activation for 0 to 30 min, the reaction was terminated. RNA was isolated and separated on denaturing gels, blotted to nylon membranes and hybridized with a 32P-labelled cDNA probe for c-fos. Messenger RNA for c-fos is detectable as early as 5-10 min following the addition of antigen and increases in a time-dependent fashion over 30 min. Unexpectedly, the addition of the hapten, 10(-4) M DNP-lysine, 5 min after the addition of antigen (which causes immediate cessation of exocytosis) does not dramatically alter the amount of message detected at 30 min. This effect is present as early as 2 min after cross-linking of the receptor and occurs at various doses of the aggregating stimulus. Thus, in contrast to the case with exocytosis and other well-described intracellular events, Fc epsilon RI-mediated increases in the level of mRNA for c-fos does not require ongoing aggregation of Fc epsilon RI.

Fc epsilon RI-mediated hydrolysis of phosphoinositides in permeable membrane vesicles

We have used hypotonic lysis of cytoplasts derived from rat basophilic leukemia (RBL) cells to prepare organelle and cytoplasm-depleted membrane vesicles called 'RBL cell ghosts' (Dreskin and Metzger, 1991). Unlike other membrane preparations, the RBL ghosts hydrolyze phosphoinositides (PIs) in response to aggregation of the high affinity receptor for IgE (Fc epsilon RI) and have proven useful for studies of the molecular events involved in transduction of this signal. A significant limitation of these preparations is that they are sealed. Thus, to incorporate membrane-impermeant molecules (such as ATP) into the intravesicular space of the ghosts, they must be added as the ghosts are formed. We have now overcome this problem by permeabilizing the ghosts with alpha-toxin from S. aureus and find that, following permeabilization, ghosts activated via Fc epsilon RI, hydrolyze PIs for a longer time than do non-permeabilized ghosts. As in the intact ghosts, this response is absolutely dependent upon ATP and is enhanced by the addition of either phosphoenolpyruvate (PEP) or creatine phosphate (CP). This report demonstrates that we can now manipulate the intravesicular environment of the RBL ghosts and extends the utility of these preparations as a model system for the study of signal transduction following activation via Fc epsilon RI.

Fc epsilon RI-mediated hydrolysis of phosphoinositides in ghosts derived from rat basophilic leukemia cells

Aggregation of the high affinity receptor for IgE (Fc epsilon RI) on mast cells by a polyvalent Ag leads to hydrolysis of phosphoinositides (PI) catalyzed by phospholipase C (PI-PLC). To understand this phenomenon in molecular terms, it is important to obtain active, cell-free preparations. In extensive preliminary studies, we could not demonstrate Fc epsilon RI-mediated activation of PI-PLC in plasma membranes prepared by conventional methods from rat basophilic leukemia cells. We now report a stepwise approach involving preparation of cytoplasts from such cells and then hypotonic lysis of the cytoplasts to obtain active membrane vesicles. These membranes, best described as "ghosts," appear to reseal after losing greater than 90% of their soluble, cytoplasmic components and contain receptors that when aggregated, activate PI-PLC to hydrolyze endogenous phospholipids. Per unit of plasma membrane, the ghosts retain approximately 25% of Fc epsilon RI-mediated stimulation of PI-PLC relative to the cells. This activity requires ATP, magnesium, phosphoenolpyruvate, and, to a limited degree, calcium. Although an adequate amount of phosphatidylinositol biphosphate is present, the predicted spike of (1,4,5)-inositol trisphosphate is not seen, and the predominant inositol phosphate isomer is (1,4)-inositol bisphosphate. This is the first report of Fc epsilon RI-mediated activation of PI-PLC in a cytoplasm-depleted system that demonstrates activation of endogenous enzyme acting on endogenous substrate. In addition, it is the first such report for any receptor of the Ig superfamily.

Fc epsilon RI-mediated hydrolysis of phosphoinositides in ghosts derived from rat basophilic leukemia cells

Aggregation of the high affinity receptor for IgE (Fc epsilon RI) on mast cells by a polyvalent Ag leads to hydrolysis of phosphoinositides (PI) catalyzed by phospholipase C (PI-PLC). To understand this phenomenon in molecular terms, it is important to obtain active, cell-free preparations. In extensive preliminary studies, we could not demonstrate Fc epsilon RI-mediated activation of PI-PLC in plasma membranes prepared by conventional methods from rat basophilic leukemia cells. We now report a stepwise approach involving preparation of cytoplasts from such cells and then hypotonic lysis of the cytoplasts to obtain active membrane vesicles. These membranes, best described as "ghosts," appear to reseal after losing greater than 90% of their soluble, cytoplasmic components and contain receptors that when aggregated, activate PI-PLC to hydrolyze endogenous phospholipids. Per unit of plasma membrane, the ghosts retain approximately 25% of Fc epsilon RI-mediated stimulation of PI-PLC relative to the cells. This activity requires ATP, magnesium, phosphoenolpyruvate, and, to a limited degree, calcium. Although an adequate amount of phosphatidylinositol biphosphate is present, the predicted spike of (1,4,5)-inositol trisphosphate is not seen, and the predominant inositol phosphate isomer is (1,4)-inositol bisphosphate. This is the first report of Fc epsilon RI-mediated activation of PI-PLC in a cytoplasm-depleted system that demonstrates activation of endogenous enzyme acting on endogenous substrate. In addition, it is the first such report for any receptor of the Ig superfamily.

A staphylococcal protein A rosetting assay for the demonstration of high affinity IgE receptors on rIL-3-dependent human basophil-like cells grown in mixed cell cultures

Mature basophils can be differentiated from other blood born cells by their morphology, metachromatically staining granules, histamine content, and the presence on their surfaces of high-affinity IgE receptors. The identification of basophil-like cells arising in mixed human bone marrow cultures, however, is made more difficult because of their immaturity and the morphologic alterations due to in vitro culture. Identification of IgE receptors on individual cells in cell preparations which could simultaneously be examined for their histochemical properties would facilitate the study of basophil growth and differentiation. Because this was difficult using existing techniques, we developed an IgE staphylococcal protein A rosetting assay which allows the identification of cells bearing high-affinity IgE receptors and permits the same cells to be examined by a variety of staining techniques. We then examined the appearance of basophil-like cells bearing IgE receptors in cultures of human bone marrow and correlated this data with measurements of IgE receptor number and affinity. The percentage of total cells grown in the presence of human recombinant IL-3 (rIL-3) that rosetted with Staphylococcus aureus increased from 2 +/- 0.5% at 1 week of culture to 7 +/- 2% at 2 weeks, 14 +/- 5% at 3 weeks, and 18 +/- 5% at 4 weeks. Using 125I-labeled IgEPS, the number of IgE receptors per rosetting basophil-like cell was calculated to be 7.3 x 10(4) at 2 weeks, 6.8 x 10(4) at 3 weeks, and 3.9 x 10(4) receptors per rosette positive basophil-like cell at 4 weeks. Finally, the rate of dissociation of IgE from these cultured cells was found to be 4.0 +/- 1.3 x 10(-5) s-1, indicating that IgE bound to IgE receptors on cultured basophil-like cells with high affinity.

IgE receptor-mediated hydrolysis of phosphoinositides by cytoplasts from rat basophilic leukemia cells

Cytoplasts (plasma membrane sacs containing cytoplasm, endoplasmic reticulum, and few organelles) were prepared from rat basophilic leukemia cells by treatment with cytochalasin B and centrifugation at 33 degrees C through stepwise gradients of Ficoll. To compare the relative ability of cytoplasts and cells to generate second-messengers (inositol phosphates, Ca2+) in response to stimulation of the high affinity receptor for IgE, we normalized our results per recovered receptor by using the tightly bound IgE as a marker. This marker correlated well with other estimates of plasma membrane recovery. Furthermore, data normalized on this basis correlated well with data expressed as percentage of phosphoinositides hydrolyzed. The purest fraction of cytoplasts (containing about 6% of the receptors) was satisfactorily devoid of organelles and, at early times, generated about 50% as much inositol phosphates per receptor as did the intact, untreated cells. This response of the cytoplasts, like that of the cells, was totally dependent upon aggregation of the receptors. The response by the cytoplasts (in the 5-min time frame which we examined), unlike that of the cells, was not enhanced by the presence of extracellular Ca2+. Furthermore, unlike the cells, the cytoplasts failed to raise their intracellular free Ca2+ levels after addition of polyvalent Ag. This result suggests that aggregation of the receptors may be insufficient, by itself, to open the normal Ca2+ channels.

IgE receptor-mediated hydrolysis of phosphoinositides by cytoplasts from rat basophilic leukemia cells

Cytoplasts (plasma membrane sacs containing cytoplasm, endoplasmic reticulum, and few organelles) were prepared from rat basophilic leukemia cells by treatment with cytochalasin B and centrifugation at 33 degrees C through stepwise gradients of Ficoll. To compare the relative ability of cytoplasts and cells to generate second-messengers (inositol phosphates, Ca2+) in response to stimulation of the high affinity receptor for IgE, we normalized our results per recovered receptor by using the tightly bound IgE as a marker. This marker correlated well with other estimates of plasma membrane recovery. Furthermore, data normalized on this basis correlated well with data expressed as percentage of phosphoinositides hydrolyzed. The purest fraction of cytoplasts (containing about 6% of the receptors) was satisfactorily devoid of organelles and, at early times, generated about 50% as much inositol phosphates per receptor as did the intact, untreated cells. This response of the cytoplasts, like that of the cells, was totally dependent upon aggregation of the receptors. The response by the cytoplasts (in the 5-min time frame which we examined), unlike that of the cells, was not enhanced by the presence of extracellular Ca2+. Furthermore, unlike the cells, the cytoplasts failed to raise their intracellular free Ca2+ levels after addition of polyvalent Ag. This result suggests that aggregation of the receptors may be insufficient, by itself, to open the normal Ca2+ channels.

IL-3-dependent growth of basophil-like cells and mastlike cells from human bone marrow

Human bone marrow cultured in the presence of human rIL-3 has been reported to give rise to basophils. In contrast, mouse bone marrow, cultured in the presence of mouse IL-3, leads to the growth of mast cells. To determine if human rIL-3 might also stimulate the growth of human mast cells, we cultured human bone marrow in the presence of human rIL-3 in suspension cultures, methylcellulose, and in "interphase" cultures where cells are layered over agar. The presence of mast cells was determined using a variety of histochemical techniques. In agreement with previous reports, basophil-like cells were identified in all culture systems. Mastlike cells were identified only in interphase cultures. By 3 wk, such cultures consisted of basophil-like cells (20 to 50%) and mastlike cells (1 to 5%). Cultures supplemented with rIL-4 showed no additional increase in basophil-like and mastlike cells. Both basophil-like and mastlike cells fluoresced with o-phthaldialdehyde and exhibited IgE receptors. Unlike basophil-like cells, mastlike cells were chloroacetate esterase, amidase, and human mast cell tryptase positive. We conclude that human rIL-3 can support the growth of human mastlike cells under selected culture conditions.

IL-3-dependent growth of basophil-like cells and mastlike cells from human bone marrow

Human bone marrow cultured in the presence of human rIL-3 has been reported to give rise to basophils. In contrast, mouse bone marrow, cultured in the presence of mouse IL-3, leads to the growth of mast cells. To determine if human rIL-3 might also stimulate the growth of human mast cells, we cultured human bone marrow in the presence of human rIL-3 in suspension cultures, methylcellulose, and in "interphase" cultures where cells are layered over agar. The presence of mast cells was determined using a variety of histochemical techniques. In agreement with previous reports, basophil-like cells were identified in all culture systems. Mastlike cells were identified only in interphase cultures. By 3 wk, such cultures consisted of basophil-like cells (20 to 50%) and mastlike cells (1 to 5%). Cultures supplemented with rIL-4 showed no additional increase in basophil-like and mastlike cells. Both basophil-like and mastlike cells fluoresced with o-phthaldialdehyde and exhibited IgE receptors. Unlike basophil-like cells, mastlike cells were chloroacetate esterase, amidase, and human mast cell tryptase positive. We conclude that human rIL-3 can support the growth of human mastlike cells under selected culture conditions.

Evolution of the hyperimmunoglobulin E and recurrent infection (HIE, JOB's) syndrome in a young girl

The hyperimmunoglobulin E and recurrent infection syndrome is difficult to diagnose in children with markedly elevated IgE and recurrent superficial Staphylococcus aureus infections who have not presented with a severe infection. The patient, the child of a woman with HIE, had elevated cord blood IgE. In early infancy, she had cutaneous colonization with S. aureus followed by frank impetiginous lesions. Anti-S. aureus IgE was easily detected with a highly specific ELISA assay at 2 years of age (2 years before her presentation with a S. aureus subcutaneous abscess). Thus, the measurement of anti-S. aureus IgE by this technique may be a useful laboratory test for the diagnosis of HIE before the appearance of a severe infection.

Metabolism of immunoglobulin E in patients with markedly elevated serum immunoglobulin E levels

The metabolism of human IgE was studied in normals, severe atopics, and patients with the hyperimmunoglobulin E-recurrent infection (HIE; Job's) syndrome to determine whether IgE metabolism is altered in patients with marked elevation of serum IgE. Purified polyclonal 125I-IgE was administered intravenously and serial plasma and urine samples were obtained. After analysis, the metabolic data support previously published evidence that IgE (at concentrations found in normal individuals) is catabolized at a higher fractional rate than other immunoglobulins and is catabolized by both an intravascular and an extravascular pathway. In addition, the data show that the fractional catabolic rate for IgE is significantly less for the atopic patients (mean +/- SEM = 0.20 +/- 0.01) and for the HIE patients (0.15 +/- 0.02) than for the normal volunteers (0.52 +/- 0.06; P less than 0.01) and is inversely related (r = -0.851; P less than 0.001) to the serum IgE concentration. These findings have specific importance in showing that decreased fractional catabolic rate contributes substantially to elevation of IgE in atopic and HIE patients. In addition, the findings have general significance in that they lead to a unifying hypothesis of immunoglobulin catabolism.

Elevated urinary histamine in the hyperimmunoglobulin E and recurrent infection (Job's) syndrome: association with eczematoid dermatitis and not with infection

To test the hypothesis that IgE-mediated release of histamine may be, in part, responsible for the abnormal inflammatory response observed in the hyperimmunoglobulin E (HIE) and recurrent infection syndrome, urine and plasma histamine levels were measured. Twenty-four-hour urinary histamine concentrations from 15 patients with HIE (23.7 +/- 6.9 micrograms/24 hr) were significantly elevated (p less than 0.001) compared to a large historical control population (10.5 +/- 0.7 micrograms/24 hr; n = 97). However, urinary histamine levels in HIE were much less abnormal (p less than 0.01) than in five patients with biopsy-proven systemic mastocytosis (159 +/- 62 micrograms/24 hr) and were not significantly elevated when levels were compared to 13 concurrently studied normal subjects (10.1 +/- 1.7 micrograms/24 hr) and nine patients with chronic granulomatous disease (8.1 +/- 1.2 micrograms/24 hr). Overall, there was no clear relationship between urine histamine values and the presence of infection as well as no significant correlation between urine histamine and total IgE or anti-Staphylococcus aureus IgE. However, urine histamine levels in a subgroup of six patients with HIE with chronic eczematoid dermatitis (42.4 +/- 12.5 micrograms/24 hr) were elevated compared with values from the historical control subjects (p less than 0.001), the concurrent control subjects (p less than 0.01), the patients with chronic granulomatous disease (p less than 0.01), and five patients with HIE who did not have skin manifestations (4.6 +/- 1.1 micrograms/24 hr; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulins in the hyperimmunoglobulin E and recurrent infection (Job's) syndrome. Deficiency of anti-Staphylococcus aureus immunoglobulin A

Patients with the hyperimmunoglobulin E and recurrent infection syndrome (HIE) characteristically have frequent skin and respiratory infections caused by Staphylococcus aureus. We have developed a set of enzyme-linked immunosorbent assays that use whole S. aureus (Wood's strain) immobilized on 0.22-micrometers filters and highly specific, affinity-purified enzyme conjugates of goat anti-human IgE, anti-human IgD, anti-human IgG, anti-human IgA, and anti-human IgM. These reagents were used to determine S. aureus-specific immunoglobulin (Ig) levels. As previously published, 10 patients with HIE had markedly higher levels of anti-S. aureus IgE than did 5 patients with eczema and recurrent superficial S. aureus infections (P less than 0.001). The HIE patients were also found to have a deficit of anti-S. aureus serum IgA as compared with 12 normal subjects, 12 patients with chronic granulomatous disease, 5 patients with chronic eczema and recurrent superficial S. aureus infections, and 3 patients with the Chediak-Higashi syndrome (P less than 0.01 for each comparison). In addition the HIE patients had an excess of anti-S. aureus IgM as compared with normal subjects (P less than 0.01). An expected excess of anti-S. aureus IgG was absent. These abnormalities cannot be explained by variations of total serum Ig levels or by a general inability to produce antigen-specific IgA because levels of naturally occurring IgA antibody against Escherichia coli lipopolysaccharide and the antigens of the pneumococcal vaccine are normal. Parotid saliva from patients with HIE contained less salivary IgA per milligram of protein (P less than 0.01) and less salivary anti-S. aureus IgA per milligram of protein (P less than 0.05) than did normal controls. The incidence of infection at mucosal surfaces and adjacent lymph nodes correlated inversely with serum anti-S. aureus IgA (r = -0.647, P = 0.034), serum anti-S. aureus IgE (r = -0.731, P = 0.016), total serum IgE (r = -0.714, P = 0.020), and total serum IgD (r = -0.597, P = 0.049). These findings are evidence of a previously undescribed immunoregulatory defect in patients with HIE, which may contribute to the increased susceptibility to infection in this syndrome.

Acute effects of growth hormone on the function of ribosomes of rat skeletal muscle

The effect of the acute intravenous administration of bovine growth hormone (bGH) to female hypophysectomized rats on the ability of ribosomes isolated from their thigh muscles to incorporate 3H-leucine and 3H-puromycin into protein in vitro was studied. Ribosomes prepared from the muscles of animals that had received bGH (200 microgram) 30 min before sacrifice were more active in incorporating leucine and puromycin into protein than the controls. However, no effect of the hormone on leucine incorporation was seen 15 min after its injection, suggesting some lag period in its course of action on ribosome function. In experiments dealing with the ability of the ribosome preparations to incorporation puromycin into protein, it was found that at the completion of the reaction, ribosomes made from the muscles of bGH-treated rats had incorporated 22% more tracer into protein than the controls, suggesting that these preparations contained a larger population of ribosomes actively engaged in protein synthesis. This conclusion was also supported by the finding that sucrose density gradient profiles of ribosome preparations from the hormone-treated rats had a greater proportion of ribosomes in the polyribosome fraction than those of the controls. From these and other observations made in this study, it would appear that the acute effect of growth hormone on the function of rat skeletal muscle ribosomes is to increase the fraction of ribosomes active in peptide synthesis.

Deoxyribonucleic acid cytophotometry of stained human leukocytes. 3. Thermal denaturation of chromatin

Thermal denaturation of chromatin has been monitored in situ in single cells using absorption cytophotometry on gallocyanin-chrome alum (GCA)-stained preparations. Spreads of human lymphocytes were fixed by ethanol freeze-substitution, digested with ribonuclease and treated at different temperatures prior to staining. Treatment in 0.15 M NaCl-0.0l5 M Na citrate (pH 7.0) for 10 min was followed by 0.15 M NaCl-0.0l5 M Na citrate (pH 7.0) with 10% formalin at the same temperature for 20 min. The GCA staining was localized to nuclei and was measured cell by cell with an integrating scanning cytophotometer. Cellular GCA stain content increased progressively with treatment temperatures above 60°C until 90°C, when it was about 1.5 times that of cells treated at 22°C. Formation of single strand deoxyribonucleic acid at different temperatures was monitored by digesting slides with an endonuclease that is specific for single strand nucleic acids and then staining with GCA. Digestion had little effect on slides that had been treated at less than 70°C, but above this temperature it caused a progressive decrease in stain content up to 90°C, when the stain content was reduced to about one-half that of undigested cells. Both with and without enzymatic digestion, these new approaches to monitoring chromatin denaturation yield preparations that are stable and can be measured on any visible light absorption cytophotometer; in addition, the enzymatic approach exemplifies a class of potential methods in which biochemical procedures are adapted to cytophotometry.