Differential requirements of B cells from normal and allergic subjects for the induction of IgE synthesis by an alloreactive T cell clone

Allergen-specific IgG+ memory B cells are temporally linked to IgE memory responses

BACKGROUND

IgE is the least abundant immunoglobulin and tightly regulated, and IgE-producing B cells are rare. The cellular origin and evolution of IgE responses are poorly understood.

OBJECTIVE

The cellular and clonal origin of IgE memory responses following mucosal allergen exposure by sublingual immunotherapy (SLIT) were investigated.

METHODS

In a randomized double-blind, placebo-controlled, time course SLIT study, PBMCs and nasal biopsy samples were collected from 40 adults with seasonal allergic rhinitis at baseline and at 4, 8, 16, 28, and 52 weeks. RNA was extracted from PBMCs, sorted B cells, and nasal biopsy samples for heavy chain variable gene repertoire sequencing. Moreover, mAbs were derived from single B-cell transcriptomes.

RESULTS

Combining heavy chain variable gene repertoire sequencing and single-cell transcriptomics yielded direct evidence of a parallel boost of 2 clonally and functionally related B-cell subsets of short-lived IgE⁺ plasmablasts and IgG⁺ memory B cells. Mucosal grass pollen allergen exposure by SLIT resulted in highly diverse IgE and IgG_E repertoires. These were extensively mutated and appeared relatively stable as per heavy chain isotype, somatic hypermutations, and clonal composition. Single IgG_E⁺ memory B-cell and IgE⁺ preplasmablast transcriptomes encoded antibodies that were specific for major grass pollen allergens and able to elicit basophil activation at very low allergen concentrations.

CONCLUSION

For the first time, we have shown that on mucosal allergen exposure, human IgE memory resides in allergen-specific IgG⁺ memory B cells. These cells rapidly switch isotype, expand into short-lived IgE⁺ plasmablasts, and serve as a potential target for therapeutic intervention.

Cytokines Involved in the Pathophysiology of IgE Response

Recent data in both mouse and human systems have clearly indicated that IL-4 plays an essential role in the induction of IgE response, whereas IFN-γ exerts an opposite effect on this phenomenon. However, IL-4 alone is unable to induce IgE synthesis. A prior membrane contact signal delivered by activated T cells is required by B cells to synthesize IgE in response to IL-4. A cognate interaction between B and T cells producing IL-4 (but not IFN-γ) is optimal for induction of IgE synthesis. However, when such IL-4 producing T cells are activated, they may provide B cells with a membrane signal, through a non-cognate interaction, which also results in induction of IgE synthesis. Other cytokines, such as IL-2 and IL-6, play an auxiliary role in IL-4 dependent IgE production.

Analyses at the clonal level of the profile of cytokine production by helper T cells have shown that imbalances between IL-4 and IFN-γ producing T cells can be detected in patients with hyperproduction of IgE. In children with hyper-IgE syndrome a strong reduction of circulating T cells able to produce IFN-γ (and TNF-α) was found, whereas both, reduction of IFN-γ-producing and increase of IL-4 producing T cells were found in patients with parasitic infestation. In allergic inflammatory infiltrates, such as those found in vernal conjuctivitis, helper T cells able to produce IL-4 and to induce IgE synthesis accounted for the large majority of infiltrating T cells. It is reasonable to suggest that systemic or microenvironmental alterations of the balance between IL-4- and IFN-γ-producing T cells may be involved, at least in part, in the pathophysiology of the increased igE response occurring in a number of human diseases.

How aluminum adjuvants could promote and enhance non-target IgE synthesis in a genetically-vulnerable sub-population

Aluminum-containing adjuvants increase the effectiveness of vaccination, but their ability to augment immune responsiveness also carries the risk of eliciting non-target responses, especially in genetically susceptible individuals. This study reviews the relevant actions of aluminum adjuvants and sources of genetic risk that can combine to adversely affect a vulnerable sub-population. Aluminum adjuvants promote oxidative stress and increase inflammasome activity, leading to the release of IL-1β, IL-18, and IL-33, but not the important regulatory cytokine IL-12. In addition, they stimulate macrophages to produce PGE₂, which also has a role in regulating immune responses. This aluminum-induced cytokine context leads to a T(H)2 immune response, characterized by the further release of IL-3, IL-4, IL-5, IL-9, IL-13, and IgE-potentiating factors such as sCD23. Genetic variants in cytokine genes, such as IL-4, IL-13, IL-33, and IL-18 influence the response to vaccines in children and are also associated with atopy. These genetic factors may therefore define a genetically-vulnerable sub-population, children with a family history of atopy, who may experience an exaggerated T(H)2 immune response to aluminum-containing vaccines. IL-4, sCD23, and IgE are common factors for both atopy and the immune-stimulating properties of aluminum adjuvants. IL-4 is critical in the production of IgE and total IgE up-regulation. IL-4 has also been reported to induce the production of sCD23 and trigger resting sIgM+, sIgD+ B-cells to switch to sIgE+ B-cells, making them targets for IgE-potentiating factors. Further, the actions of IgE-potentiating factors on sIgE+ B-cells are polyclonal and unrestricted, triggering their differentiation into IgE-forming plasma cells. These actions provide a mechanism for aluminum-adjuvant promotion and enhancement of non-target IgE in a genetically vulnerable sub-population. Identification of these individuals may decrease the risk of adverse events associated with the use of aluminum-containing vaccines.

Immune response to hepatitis B vaccine in asthmatic children

Asthma is a disease that demonstrates chronic Th2 lymphocyte-mediated pulmonary inflammation. We hypothesized that cytokines produced by asthmatic lung inflammation bias the immune response to antigens administered systemically toward a Th2 response, as assessed by serum IgE antibody and lymphocyte-secreted IL-4 and IL-5. We also hypothesized that treatment of asthmatic children with local anti-inflammatory agents reduces this cytokine-mediated Th2 influence. We systemically immunized groups of asthmatic children (n=29) who were participating in a long-term, randomized, placebo-controlled clinical trial of inhaled anti-inflammatory therapy (Childhood Asthma Management Program) and nonasthmatic children (n=12) with hepatitis B (Hep B) antigen, and examined their antigen-specific antibody and lymphocyte cytokine secretion profiles. The asthmatic population demonstrated an increased amount of Th2-mediated serum IgE anti-Hep B antibody, as compared to nonasthmatic children; but comparable amounts of IgG1, IgG2, IgG3, IgA, and IgM anti-Hep B antibody and lymphocyte IFNgamma, IL4, and IL5. There was no significant difference of antibody isotype or cytokine production between asthmatic subjects receiving treatment with budesonide or nedocromil, as compared to placebo. In conclusion, there is a subtle bias in responses to systemic immunization in children with asthma, but anti-inflammatory therapy does not affect this bias. The findings support the concept that the Th2 bias may be largely genetic. Importantly, we confirmed that children with asthma, including even those on inhaled corticosteroids, responded to Hep B immunization as well as did nonasthmatic children with the major isotypes of anti-Hep B antibody, suggesting that vaccine protection against hepatitis B is not influenced by inhaled steroid therapy.

Bystander T cells participate in specific response to cockroach antigen (CR) in vitro

Allergic reactions due to whole body, body parts and fecal products of cockroach (CR) are characterized by inflammatory reaction that may lead to symptoms of rhinitis or asthma in atopic individuals. Although the majority of T cells at the site of CR hypersensitivity are not antigen specific, the cellular subset and cytokine receptors that participate and control the outcome of the reaction have not been fully studied. In this study, we have used fluorescent activated cell sorter (FACS) analysis to characterize the activation marker and cytokine profile of antigen specific and bystander T cells after in vitro stimulation of peripheral blood lymphocytes with whole body extract of CR antigen. There was significant enhancement of CD69 on blast and bystander T cells in all atopic subjects compared to non-atopics. Both antigen specific and bystander T cells showed increased expression of HLA-DR, CD25 and CD71 in 9 of 11 atopic patients compared to control. There was also an increase in CD45RA+ and a decrease in CD45RO+ cells following antigen stimulation. These results correlated with the increase in the early apoptotic cells observed in patients as measured by Annexin V stain. Our data revealed that there was no difference in the expression of CD95 in both stimulated and bystander T cells. However, there was enhancement of FasL by CR antigen, suggesting that the increased apoptosis that was observed was probably due to the Fas/FasL interaction. Positive intracellular IL2, IL-4 and IFN-gamma in T cells were observed in only the antigen specific blast cells in 83% of patients studied. These results suggest interplay of memory T cell response, apoptosis, and activated bystander T cells activities in maintaining cellular homeostasis during allergic reaction in cockroach sensitive atopic subjects.

IgE responses to bluetongue virus (BTV) serotype 11 after immunization with inactivated BTV and challenge infection

To test the hypothesis that development of a BTV-specific IgE response plays a role in clinical disease manifestation, the humoral immune response of cattle to inactivated and virulent BTV was studied. Three calves received three sensitizing immunizations of inactivated BTV, 3 weeks apart. The BTV-sensitized animals, two non-sensitized BTV-seropositive and 4 BTV-seronegative control cattle. were challenge-exposed with BTV-11, UC8 strain. All cattle inoculated with inactivated BTV developed group-specific non-neutralizing and serotype-specific neutralizing antibodies. The development of post-challenge-exposure neutralizing antibody titers was inversely correlated with protective immunity. None of the BTV-challenged animals showed clinical disease. The levels of IgE were greatest in the sensitized calves after virus challenge in comparison with control groups. The sequential development, specificity and intensity of virus protein-specific humoral responses were evaluated using immunostaining. After challenge exposure of BTV-sensitized and non-sensitized cattle, total and IgE antibodies reacted consistently within BTV structural proteins VP2, VP5 and VP7. Although no correlation was found between clinical disease and IgE, results add support to the hypothesis that IgE may be involved in the pathogenesis of clinical disease, since infection with BTV causes an increase in serum IgE levels. However, these results suggest that the levels of virus-specific reactivity may be an important factor in determining whether or not clinical disease manifestation occurs.

Role of JAK3 in CD40-Mediated Signaling

CD40 is a member of the tumor necrosis factor receptor family and plays an important role in B-cell survival, growth, differentiation, and isotype switching. Recently, CD40 has been shown to associate with JAK3, a member of the family of Janus Kinases, which are nonreceptor protein kinases involved in intracellular signaling mediated by cytokines and growth factors. To investigate the role of JAK3 in CD40-mediated signaling, we studied the effect of CD40 stimulation on B-cell proliferation, IgE isotype switching, and upregulation of surface expression of CD23, ICAM-1, CD80, and LT-α in JAK3-deficient patients. Our studies show that stimulation of B cells with monoclonal antibody to CD40 in the presence of interleukin-4 (IL-4) or IL-13 resulted in similar responses in JAK3-deficient patients and normal controls. This suggests that JAK3 is not essential for CD40-mediated B-cell proliferation, isotype switching, and upregulation of CD23, ICAM-1, CD80, and LT-α surface expression.

Role of JAK3 in CD40-Mediated Signaling

CD40 is a member of the tumor necrosis factor receptor family and plays an important role in B-cell survival, growth, differentiation, and isotype switching. Recently, CD40 has been shown to associate with JAK3, a member of the family of Janus Kinases, which are nonreceptor protein kinases involved in intracellular signaling mediated by cytokines and growth factors. To investigate the role of JAK3 in CD40-mediated signaling, we studied the effect of CD40 stimulation on B-cell proliferation, IgE isotype switching, and upregulation of surface expression of CD23, ICAM-1, CD80, and LT-α in JAK3-deficient patients. Our studies show that stimulation of B cells with monoclonal antibody to CD40 in the presence of interleukin-4 (IL-4) or IL-13 resulted in similar responses in JAK3-deficient patients and normal controls. This suggests that JAK3 is not essential for CD40-mediated B-cell proliferation, isotype switching, and upregulation of CD23, ICAM-1, CD80, and LT-α surface expression.

Mechanisms of inhibition of IgE synthesis by nedocromil sodium: nedocromil sodium inhibits deletional switch recombination in human B cells

IgE synthesis requires IL-4 and a T cell-B cell interaction that involves the B-cell antigen CD40 and its ligand expressed on activated T cells. Nedocromil sodium (NS), an effective prophylactic agent in asthma, inhibits IgE synthesis by human B cells. In this report we examined the mechanisms of this inhibition. NS targeted the B cells because it inhibited IgE synthesis induced by anti-CD40 and IL-4 in highly purified B cells (greater than 98% CD19+). NS had no effect on the induction of epsilon-germline transcripts by IL-4 but strongly inhibited CD40-mediated S mu --> S epsilon deletional switch recombination. The effect of NS was not specific for CD40 because it inhibited IgE synthesis in B cells stimulated with hydrocortisone plus IL-4. Moreover, the effect of NS was not specific for IgE because it inhibited CD40/IL-4-driven IgG4 synthesis by B cells sorted for lack of surface expression of IgG4. NS caused only modest inhibition of spontaneous IgE synthesis by B cells from patients with hyper-IgE syndrome, suggesting that it has little effect on B cells that have already undergone isotype switching. These results strongly suggest that NS inhibits IgE isotype switching by inhibiting deletional switch recombination and that NS has a novel potential mechanism for the prevention of asthma and other allergic diseases.

Interleukin-4 receptor expression by human B cells: functional analysis with a human interleukin-4 toxin, DAB389IL-4

BACKGROUND

Studies of human IgE-secreting B cells have proven difficult because of the small size of this population. We have used an interleukin-4 (IL-4) fusion toxin to detect functionally IL-4 receptor (IL-4R) expression on B cells involved in IgE synthesis.

METHODS

In diphtheria toxin IL-4 (DAB389IL-4) the receptor-binding domain of diphtheria toxin has been replaced with human IL-4. DAB389IL-4 cytotoxicity depends on IL-4R binding and internalization.

RESULTS

Addition of DAB389IL-4 inhibited IgE synthesis induced by IL-4+ anti-CD40 monoclonal antibody or hydrocortisone. IgE inhibition resulted from DAB389IL-4 B-cell cytotoxicity because DAB389IL-4 inhibited IL-4-independent B-cell proliferation. Thus induction of human IgE synthesis involves IL-4R+ cells. In contrast, terminally differentiated, IgE-producing B cells no longer express functional IL-4R because DAB389IL-4 only modestly inhibited ongoing IgE synthesis by B cells from patients with hyper-IgE states and only minimally affected IL-4-induced IgE synthesis in normal B cells when the toxin was added at day 7. Pokeweed mitogen-induced IgM synthesis was sensitive to early but not to late addition of DAB389IL-4. Thus the loss of functional IL-4R immunoglobulin-secreting B cells is independent of isotype switching.

CONCLUSIONS

IgE-secreting B cells no longer express functional IL-4R. Therapies for allergic disease that target the IL-4R would not affect IgE-secreting B cells but may block the recruitment of B cells into the IgE-secreting pool. For optimal benefits this approach may be combined with therapies that target IL-4R-, IgE-secreting B cells.

Role of protein tyrosine kinases and phosphatases in isotype switching: crosslinking CD45 to CD40 inhibits IgE isotype switching in human B cells

Protein tyrosine kinases and protein tyrosine phosphatases play an important role in the transduction of signals via antigen receptors in T and B cells, and in CD40-dependent B-cell activation. To examine the role of tyrosine kinases and phosphatases in B-cell isotype switching, we examined the effects of the engagement of the transmembrane phosphatase CD45 on the synthesis of IgE induced by IL-4 and anti-CD40 monoclonal antibody (mAb). Crosslinking CD45 to CD40 using biotinylated mAbs and avidin strongly inhibited CD40-mediated IgE synthesis in IL-4-treated human B cells. CD40/CD45 crosslinking did not affect epsilon germline transcription in B cells stimulated with IL-4, but strongly inhibited induction of S mu/S epsilon switch recombination as detected by a nested primer polymerase chain reaction assay. The B-cell src-type tyrosine kinase lyn, which is activated following CD40 engagement, is a potential target for the effects of CD45 observed in our experiments, because CD45/CD40 crosslinking resulted in the inhibition of CD40-mediated lyn phosphorylation and activation. These results suggest an important role for protein tyrosine kinases and phosphatases in CD40-mediated induction of isotype switching to IgE.

Role of protein tyrosine kinases in CD40/interleukin-4-mediated isotype switching to IgE

The B-cell antigen CD40 transduces signals, which synergize with interleukin (IL)-4 to induce IgE synthesis in human B cells. IL-4 induces epsilon germline transcription but not mature epsilon transcripts or IgE protein synthesis in B cells. Addition of anti-CD40 monoclonal antibody to IL-4-treated B cells results in deletional S mu--> S epsilon switch recombination, expression of mature epsilon transcripts, and IgE synthesis and secretion. Because both IL-4 and anti-CD40 induce protein tyrosine phosphorylation in B cells, we investigated the role of protein tyrosine kinase in IL-4/CD40-mediated IgE synthesis. The protein tyrosine kinase inhibitors genistein and herbimycin A, but not the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) or the protein kinase A inhibitor N-2-guanidinoethyl-5-isoquinolinesulfonamide, inhibited IgE synthesis in B cells stimulated with IL-4 and CD40. Genestein and herbimycin, but not H7, inhibited IL-4-driven epsilon germline transcription in B cells. Both genestein and herbimycin, but not H7, inhibited CD40-mediated IgE synthesis in B cells pretreated for 4 days with IL-4 to allow optimal expression of epsilon germline transcripts. Inhibition of IgE synthesis in these cultures was accompanied by inhibition of S mu--> S epsilon deletional switch recombination as assayed by nested polymerase chain reactions. These results suggest that activation of protein tyrosine kinase plays an important role in both the IL-4 and the CD40 signalling pathways that lead to IgE isotype switching in B cells.

Disodium cromoglycate inhibits S mu-->S epsilon deletional switch recombination and IgE synthesis in human B cells

IgE synthesis requires interleukin 4 (IL-4) and a T-B cell interaction that involves the B cell antigen CD40 and its ligand expressed on activated T cells. IL-4 induces epsilon germline transcription whereas ligation of CD40 results in deletional S mu-->S epsilon switch recombination, expression of mature epsilon transcripts, and IgE synthesis and secretion. We demonstrate that disodium cromoglycate (DSCG), a drug commonly used for the prophylactic treatment of allergic disease, inhibits T cell-driven IgE synthesis by human B cells at concentrations readily achievable in the course of inhaled therapy for asthma. Inhibition of IgE synthesis by DSCG was not the result of drug toxicity because DSCG did not affect the viability of T and B cells or their proliferation to mitogens. DSCG did not interfere with CD40 ligand expression by T cells but clearly targeted the B cells because it inhibited IgE synthesis induced by anti-CD40 and IL-4 in populations of highly purified B cells. DSCG had no effect on the induction of epsilon germline transcripts by IL-4 but strongly inhibited CD40 mediated S mu-->S epsilon deletional switch recombination in IL-4-treated B cells as assayed by nested primer PCR. The effect of DSCG was not specific for CD40-mediated induction of IgE isotype switching because DSCG inhibited IgE synthesis as well as S mu-->S epsilon deletional switch recombination induced by hydrocortisone and IL-4 in B cells. Moreover, the effect of DSCG was not specific for IgE isotype switching because DSCG inhibited the synthesis of IgG4 by B cells sorted for lack of surface expression of IgG4 and stimulated with anti-CD40 and IL-4. DSCG caused only minimal inhibition (< 15%) of spontaneous IgE synthesis by lymphocytes from patients with the hyper-IgE syndrome and did not affect pokeweed mitogen-induced IgG and IgA synthesis by lymphocytes suggesting that it has little effect on B cells that have already undergone isotype switching. These results indicate that DSCG inhibits switching to IgE in B cells and suggest a novel potential mechanism for the prevention of allergic disease by DSCG.

The repertoire of rheumatoid factor-producing B cells in normal subjects and patients with rheumatoid arthritis

OBJECTIVE

To compare the B cell repertoire of normal individuals and patients with rheumatoid arthritis (RA) and, specifically, to identify precursor B cells with the potential to secrete rheumatoid factor (RF) and to understand the T helper cell requirements for the production of this autoantibody.

METHODS

Frequencies of precursors of IgM-, IgG-, and RF-producing B cells were measured in a limiting-dilution system. Two distinct sources of T cell help were compared. T cell help was provided by anti-CD3-activated CD4+ human T cell clones, or T cell-B cell interaction was facilitated by the bacterial super-antigen staphylococcal enterotoxin D (SED).

RESULTS

A subset of 2-14% of peripheral blood B cells secreted IgM and IgG in SED-driven cultures. The SED-responsive B cell subpopulation was present at 10 times higher frequency in normal donors compared with RA patients. However, the repertoires were very similar, particularly for RF+ precursors, which represented approximately one-third of all SED-responsive B cells. In normal individuals, most of these RF+ precursor B cells did not respond to anti-CD3-activated T helper cells, with only a very small fraction of B cells activated by anti-CD3-driven helper cells maturing into RF-secreting B cells (from 1 of 182 to 1 of 889 IgM-producing B cells). This subset was expanded approximately 50-fold in RA patients.

CONCLUSION

Normal subjects and RA patients share a pool of B cells which secrete RF when activated in the presence of SED and T helper cells. These B cells are frequent and obviously anergic in normal individuals. The B cell subset with the potential to produce RF when help is provided in noncognate T-B interaction (anti-CD3-driven T cells) is considerably expanded in RA patients, probably reflecting an increased responsiveness of such B cells to helper signals.

Interferon (IFN)-alpha, IFN-gamma, interleukin (IL)-2, and arachidonic acid metabolites modulate IL-4-induced IgE synthesis similarly in healthy persons and in atopic dermatitis patients

The role of cytokines and arachidonic acid metabolites in the regulation of IgE production in healthy persons and in atopic dermatitis patients with elevated IgE levels was studied. Interleukin-4 (IL-4) induced IgE production in peripheral blood mononuclear cells (PBMCs) of all donors, and no significant difference was found between the amounts of IgE produced by healthy persons and atopic dermatitis patients. Similarly, recombinant interferon (IFN)-alpha and IFN-gamma, as well as IL-2, inhibited IL-4-induced IgE production to a similar extent in both study groups. To evaluate the role of arachidonic acid (AA) metabolites in the regulation of IgE production, we added indomethacin, an inhibitor of the cyclooxygenase pathway, or nordihydroguaiaretic acid (NDGA), an inhibitor of the lipoxygenase pathway, to IL-4-treated cultures. Both indomethacin and NDGA strongly inhibited IL-4-induced IgE production. They also inhibited IL-4-induced IgG4 synthesis. No significant difference in the amount of inhibition was found between the two study groups. We were unable to restore the NDGA-induced inhibition of IgE-production by adding leukotrienes B4, C4, D4, or 5-HETE to the NDGA-treated cultures. PGE2 also failed to restore the indomethacin-mediated inhibitory effect. Consequently, NDGA- and indomethacin-mediated inhibitory effects do not appear to be mediated by any single factor studied. Collectively, our results show IFNs and IL-2 to be similar in effect in the modulation of IL-4-induced IgE synthesis in healthy and atopic persons.(ABSTRACT TRUNCATED AT 250 WORDS)

An ultrasensitive system to detect IL-4: enzyme-linked immunosorbent assay (ELISA) combined with an avidin-biotin and enzyme amplification system

We established an ultrasensitive interleukin-4 enzyme-linked immunosorbent assay by combining ELISA with an avidin-biotin and enzyme amplification system. The resultant system (AB-EA ELISA) was 250 times more sensitive than conventional ELISA and 2.5 times more sensitive than enhanced ELISA using an enzyme amplification system alone. The ultrasensitive assay was specific to IL-4 alone; there was no cross reaction with other cytokines. Using the ultrasensitive assay, we measured IL-4 synthesis in vitro by unstimulated and stimulated peripheral blood mononuclear cells (PBMC) from patients with allergic rhinitis. PBMC from patients spontaneously produced measurable amounts of IL-4, whereas IL-4 production from PBMC of normal controls, if any, was below detectable levels. Stimulation of the cultures with LPS significantly increased IL-4 production in two of six patient PBMC cultures but in none of the control cultures; stimulation with Con A markedly increased IL-4 production in all patient PBMC cultures but in only two of seven control cultures. These results suggest that the AB-EA ELISA is a useful method to study the mechanism of IL-4 synthesis in type-I allergic diseases.

T cells from atopic individuals produce IgE-inducing activity incompletely blocked by anti-interleukin-4 antibody

We investigated peripheral blood B and T lymphocyte functions in atopic individuals. B cells were co-cultured with mutant EL4 thymoma cells in the presence of a standard T cell supernatant (T-SN) with or without exogenous interleukin (IL)-4. IgE secretion in this assay was found to be IL-4 dependent, but not significantly different for atopic patients (n = 25) vs. normal controls (n = 25). Phytohemagglutinin plus phorbol 12-myristate 13-acetate (PHA+PMA)- induced T-SN from patients or controls was tested on normal B cells in the same assay system (in the absence of exogenous IL-4). Compared to the controls, the IgE-inducing activity was significantly increased for patients with asthma or allergic rhinitis (n = 12; p less than 0.005) but not for patients with atopic dermatitis (n = 13). The difference between the asthma or allergic rhinitis vs. the atopic dermatitis groups was significant (p greater than 0.05). Since the assay was not inhibited by interferon (IFN)-gamma, this difference can not be attributed to IFN-gamma concentrations. Other T cell activities may be different between the patient groups or atopic T cells from the respiratory mucosa may recirculate more than those from the skin. In any case, the T cells rather than the B cells were found to be abnormal in atopic individuals. If atopic T cells were stimulated with PHA+PMA not as immediately but after a resting period of 48 h in culture medium alone, the IgE-inducing activity, but not the total Ig-inducing activity or the IL-2 secretion, disappeared. In addition, a mean of 37% of the IgE-inducing activity (range of 13% to 79% for five very active T-SN) was not inhibited by an anti-IL-4 antibody which neutralized exogenous IL-4, indicating a participation of factors capable of bypassing the requirement for IL-4 for the IgE response.

Deletional switch recombination occurs in interleukin-4-induced isotype switching to IgE expression by human B cells

There is controversy as to whether deletional rearrangement occurs between the IgM and IgE switch regions (S mu and S epsilon, respectively) during switching to the IgE isotype. We have addressed the issue by stimulating normal human B cells, sorted for lack of expression of surface IgE, to produce IgE by infection with Epstein-Barr virus (EBV) in the presence of interleukin 4 (IL-4). Genomic DNA was amplified for S mu/S epsilon switch junction fragments by utilizing the nested-primer polymerase chain reaction. Switch junction fragments were amplified from B cells infected with EBV in the presence of IL-4 but not from B cells infected with EBV alone. The DNA sequence of these "switch fragments" revealed direct joining of S mu to S epsilon in each case. The recombination sites within S mu were clustered within 900 base pairs at the 5' end of the switch region, suggesting that there are "hot spots" for recombination within S mu. The S epsilon recombination sites were scattered throughout the S epsilon region. These findings indicate that IL-4-induced isotype switching to IgE production in human B cells is accompanied by DNA rearrangements with joining of S mu to S epsilon.

Regulation and deregulation of human IgE synthesis

The IgE antibody system is among the most sophisticated of immune defense mechanisms. IgE molecules bind specifically and avidly to receptors localized on the surface of tissue mast cells and circulating basophils. These cells can produce and release several potent mediators after antigen interaction with a small number of surface-bound IgE molecules. The enormous amplification power of the IgE antibody system not only provides an important defense mechanism against parasites, but is also responsible for a number of clinical disorders. The human pathological condition most commonly associated with hyperproduction of IgE is atopy, the familial allergic disorder of immediate-type hypersensitivity to environmental allergens. In this paper Sergio Romagnani summarizes current understanding of the mechanisms involved in IgE regulation. Such studies are of primary importance in defining alterations responsible for the pathological conditions characterized by hyperproduction of IgE.

The immune complex: possible ways of regulating the antibody response

B cells express antigen, Fc and complement receptors on their surfaces and can thus bind all three components of an immune complex. In addition to the direct effects that they exert on cells, immune complexes may affect localization, presentation and digestion of antigen. In this article, Birgitta Heyman discusses recent developments in antibody-mediated regulation of the humoral immune response, with emphasis on in vivo systems where antigens are injected together with highly purified IgM or IgG antibodies in the absence of adjuvants.

Cytokine regulation of antigen-driven immunoglobulin production in filarial parasite infections in humans

To define the immunoregulatory mechanisms underlying serum IgE levels found in patients with filariasis, we studied polyclonal IgE production by peripheral blood mononuclear cells (PBMC) from 15 patients with filarial infections, with a focus on the role of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) in the generation and regulation of the response. Spontaneous in vitro IgE production was elevated in 10 of the 15 patients (836-6,464 pg/ml; normals, less than 500 pg/ml). Addition of filarial parasite antigen to PBMC cultures significantly stimulated polyclonal IgE production in an antigen dose-dependent manner in 10 of 12 patients tested (P less than 0.001). The essential role of IL-4 in the generation of this response was demonstrated when simultaneous addition of anti-IL-4 completely inhibited antigen-stimulated IgE production in all 10 patients studied. An inhibitory role of endogenously produced IFN-gamma was also indicated when the addition of anti-IFN-gamma to the cultures significantly augmented filarial antigen-stimulated IgE production by 33-1,238% in these same patients. Addition of 10-1,000 U/ml of recombinant human IFN-gamma to PBMC completely inhibited parasite antigen-induced IgE production. This study demonstrates that filarial antigen-stimulated IgE production in patients with filariasis is mediated by IL-4 and down regulated by IFN-gamma and suggests that the amount of IgE produced depends on the relative quantity of IL-4 and IFN-gamma generated by parasite-specific T cells.

Regulation of immunoglobulin (Ig)E synthesis in the hyper-IgE syndrome

The hyper-IgE (HIE) syndrome is characterized by high IgE serum levels, chronic dermatitis, and recurrent infections. The mechanisms responsible for hyperproduction of IgE in HIE patients are presently unknown. We investigated whether spontaneous in vitro IgE synthesis by PBMC from seven HIE patients was sensitive to signals (cell adhesion, T/B cell cognate interaction and lymphokines: IL-4, IL-6, and IFN-gamma) known to regulate IgE induction in normals. Our results show that, unlike IL-4 dependent IgE synthesis induced in normals, spontaneous IgE production by PBMC from HIE patients was not blocked by monoclonal antibodies to CD2, CD4, CD3, and MHC class II antigens. Furthermore, antibodies to IL-4 and IL-6 did not significantly suppress IgE production. IFN-gamma had no significant effects on spontaneous in vitro IgE synthesis. To test whether an imbalance in lymphokine production might underlie hyperproduction of IgE in HIE patients, mitogen-induced secretion of IL-4 and IFN-gamma by PBMC was assessed. No significant difference was detected between HIE patients and normal controls. Thus, ongoing IgE synthesis in the HIE syndrome is largely independent of cell-cell interactions and endogenous lymphokines, and is due to a terminally differentiated B cell population, no longer sensitive to regulatory signals.

T- and B-cell dysregulation of IgE synthesis in cystic fibrosis patients with allergic bronchopulmonary aspergillosis

Since Aspergillus fumigatus (Af)-specific and polyclonal serum IgE levels are characteristically elevated in patients with allergic bronchopulmonary aspergillosis (ABPA), we evaluated in vitro regulation of IgE synthesis in cystic fibrosis (CF) patients with ABPA. We studied 11 CF patients with ABPA, 37 patients with positive Af prick skin tests and/or IgG precipitating antibodies (ST/PPT+), and 35 patients with no humoral or skin responses to Aspergillus (ST/PPT-). Mean serum IgE concentration was significantly elevated in CF subjects with ABPA compared to ST/PPT+ and ST/PPT- patients, 2866 vs 303 and 61 IU/ml, respectively (P less than 0.01). In vitro studies demonstrated that ABPA patients' B cells spontaneously synthesized significantly increased amounts of IgE compared to ST/PPT positive and negative subjects, 1980 vs 220 and 13 pg/ml, respectively (P less than 0.01). In addition, preformed B-cell-associated IgE was also significantly elevated in ABPA subjects (P less than 0.01), indicating prior in vivo activation. Supernatant cultures of Af-stimulated T cells from ABPA subjects significantly induced allogeneic B-cell IgE synthesis compared to ST/PPT positive and negative CF subjects, 206 vs 13 and 4 pg/ml, respectively (P less than 0.01). Thus T cells stimulated with Aspergillus antigens secrete cytokines that induce B-cell IgE synthesis in ABPA subjects. B-cell IgE hyperactivity is manifested by in vivo and in vitro increased IgE concentrations. Analyses of T-cell regulation and B-cell IgE synthesis distinguish CF subjects with ABPA from Aspergillus sensitive non-ABPA subjects.

The staphylococcal toxic shock syndrome toxin 1 triggers B cell proliferation and differentiation via major histocompatibility complex-unrestricted cognate T/B cell interaction

The Staphylococcus aureus exotoxin toxic shock syndrome toxin 1 (TSST-1) is a potent activator of T cells and monocytes. We have recently demonstrated that TSST-1 is a superantigen that binds monomorphic determinants on MHC class II molecules. In the present study, we have examined the effect of TSST-1 on the activation and differentiation of high density human tonsillar B cells. TSST-1 bound to tonsilar B cells with high affinity and saturation kinetics. This binding was effectively inhibited by a combination of anti-HLA-DR and anti-HLA-DQ mAbs. Treatment of purified B cells with TSST-1 failed to induce B cell proliferation or Ig production. However, in the presence of irradiated T cells, TSST-1 induced resting B cells to proliferate and differentiate into Ig secretory cells. TSST-1 mimicked nominal antigen in that its induction of B cell responses was strictly dependent on physical contact between T and B cells, and was profoundly inhibited by anti-MHC class II mAbs, anti-CD3 mAbs, and, to a lesser extent, by anti-CD18 mAbs. However, unlike nominal antigen, TSST-1-mediated T/B cell interactions were MHC unrestricted. These results suggest that TSST-1 induces T cell-dependent B cell proliferation and differentiation by virtue of its ability to mediate MHC-unrestricted cognate T/B cell interaction via the TCR/CD3 complex and MHC class II antigens.

Regulation of immunoglobulin production in hyperimmunoglobulin E recurrent-infection syndrome by interferon gamma

The hyperimmunoglobulin E recurrent-infection (Job) syndrome (HIE) is a congenital disorder characterized by high serum IgE, chronic eczematoid dermatitis, and recurrent infections. We examined the effect of interferon gamma (IFN-gamma) on excessive IgE production in HIE patients. Spontaneous in vitro production of IgE by peripheral blood mononuclear cells from HIE patients was elevated compared to normal individuals and correlated with serum IgE. In 9 of 13 patients, IgE production by peripheral blood mononuclear cells was inhibited by 50% by IFN-gamma at 100-1000 units/ml, whereas inhibition by IFN-gamma at 10(4) units/ml ranged from 67 to 93% for these 9 patients. IFN-gamma also inhibited IgG1, IgG3, and IgG4 production by B lymphocytes without inhibiting IgG2 production. IFN-gamma was administered subcutaneously to 5 HIE patients. After 2 weeks of treatment with IFN-gamma (0.05 mg/m2) at three doses per week given on alternate days, peripheral blood mononuclear cells from all 5 HIE patients decreased spontaneous in vitro IgE production (27-62% decrease) with no change in IgG and IgM. One patient had a 58% decrease in serum IgE and another patient had a 50% decrease in serum IgE after the IFN-gamma was increased to 0.1 mg/m2 for three doses per week for a month. In both patients, serum IgE returned to pre-IFN-gamma-challenge levels 1-3 months after completion of treatment, and in vivo IFN-gamma did not affect serum IgG and IgM, although serum IgG4 decreased with changes in serum IgE. Our studies demonstrate that IFN-gamma can regulate production of IgE and some IgG subclasses in humans.

Role for T cells, IL-2 and IL-6 in the IL-4-dependent in vitro human IgE synthesis

The role of T cells and monocytes, as well as that of cytokines, such as IL-1, IL-2 and IL-6, on the IL-4-dependent in vitro human IgE synthesis was investigated. Recombinant IL-4, IL-4-containing T-cell clone supernatants and different combinations of recombinant cytokines failed to induce highly purified B cells to synthesize IgE. IL-4-dependent IgE synthesis was restored by addition to purified B cells of either untreated or mitomycin C-treated autologous T lymphocytes. Addition to purified B cells of autologous monocytes did not restore the IgE response, but usually it exerted a potentiating effect on the synthesis of IgE induced by IL-4 in the presence of suboptimal concentrations of T cells. The activity of T cells apparently preceded that of IL-4 and required a physical contact with B cells. The presence in culture of IL-2 also appeared to be necessary for the T-cell and IL-4-dependent IgE synthesis. Even though not essential, IL-6 was able to potentiate IgE synthesis in most experiments, whereas IL-1 did not display any modulatory effect.

Induction of human IgE synthesis by CD4+ T cell clones. Requirement for interleukin 4 and low molecular weight B cell growth factor

We have analyzed in detail the precise requirements for the induction of human IgE synthesis using several experimental approaches with purified B cells and well-characterized alloantigen-specific CD4+ T cell clones expressing different profiles of lymphokine secretion. Using these clones under cognate conditions in which the B cells expressed alloantigens recognized by the cloned T cells, we have confirmed that IL-4 is required for the induction of IgE synthesis, but we have clearly demonstrated that IL-4 by itself is not sufficient. With several cloned CD4+ T cell lines, including an IL-4-producing clone that could not induce IgE synthesis, and cloned T cells pretreated with cyclosporin A to inhibit lymphokine synthesis, we showed that Th cell-B cell interactions are necessary for IgE synthesis, and that low molecular weight B cell growth factor (LMW-BCGF) and IL-4, in combination, are lymphokines of major importance in the induction of IgE synthesis. Together our results indicate that optimal induction of an IgE-specific response requires the exposure of B cells to a particular complex of signals that include (a) a signal(s) involving Th-B cell interaction that primes B cells to receive additional signals from soluble lymphokines, (b) a specific B cell proliferative signal provided by LMW-BCGF, and (c) a specific B cell differentiation signal provided by IL-4.

Endogenous interleukin 6 plays an obligatory role in interleukin 4-dependent human IgE synthesis

The lymphokine interleukin (IL) 4 plays a crucial role in the regulation of IgE synthesis. In the present study, the cellular and cytokine requirements for the IL4-dependent induction of IgE synthesis in humans were analyzed. Recombinant IL4 could induce IgE synthesis by peripheral blood mononuclear cells and autologous T/B cell mixtures, but not by highly purified B cells. IgE induction by IL4 was strongly decreased in monocyte-depleted peripheral blood mononuclear cells. These results show that the induction of IgE synthesis by recombinant IL4 is T cell dependent and optimal in the presence of monocytes. IL5 and IL6, but not IL2, IL1 and tumor necrosis factor-alpha, strongly up-regulated the IL4-dependent synthesis of IgE, with modest effects on cell proliferation. An anti-IL6 polyclonal antibody strongly inhibited IL4-driven IgE production. Endogenous IL6 plays, therefore, an obligatory role in the IL4-dependent induction of IgE. However, a combination of IL4, IL5 and IL6 (with or without IL1) at optimal concentrations could not induce IgE synthesis by purified normal B cells, indicating that cytokine-mediated signals, although essential, are not sufficient for the IL4-dependent induction of IgE synthesis.

The role of allergy and nonspecific airway hyperresponsiveness in the pathogenesis of chronic obstructive pulmonary disease

Although the information that has been reviewed leaves many questions unanswered, some conclusions can be drawn from available data. (1) Smoking appears to increase the risk of sensitization to certain inhaled antigens encountered in the workplace; however, there is no definite evidence that smoking increases the frequency or intensity of allergy to common aeroallergens in the general population. On average, smokers have higher serum total IgE concentrations and blood eosinophil counts than do nonsmokers, but the mechanisms underlying these alterations are not clear. Analysis of these relationships is complicated by observations suggesting that atopic persons are less likely to become and to remain regular cigarette smokers. (2) Long-term cigarette smoking may be associated with increased nonspecific airway responsiveness, although the magnitude of this effect is relatively small when one adjusts for prechallenge level of pulmonary function. This effect of smoking may be more pronounced in atopic persons. (3) Atopy, as assessed by skin testing and serum IgE concentrations, is associated with asthma, nonspecific airway hyperresponsiveness, and reduced pulmonary function level in population data. However, there is no clear evidence that atopy is a risk factor for irreversible airflow obstruction in persons without asthma. Population data do not indicate how much of the reduction in pulmonary function associated with atopy and asthma is potentially reversible. (4) Blood eosinophil count appears inversely related to the level of pulmonary function and directly related to the rate of decline of pulmonary function among nonsmokers. Reports vary concerning whether the relationship of eosinophil count to level of pulmonary function remains after excluding subjects with diagnosed asthma. This relationship may be determined largely by a clinically distinguishable subset of nonsmokers with "asthmatic bronchitis." Presumably, these observations reflect an adverse impact of eosinophilic inflammation in the airways or lung parenchyma. It is not clear whether this represents an allergic response because skin-test reactivity to common aeroallergens and serum total IgE concentration do not show similar relationships to reduced level and rapid decline of pulmonary function. (5) Among smokers, nonspecific airway hyperresponsiveness appears to be associated with an accelerated longitudinal decline of pulmonary function, although most studies indicating this association are limited by either a retrospective design or lack of adjustment for prechallenge level of pulmonary function.(ABSTRACT TRUNCATED AT 400 WORDS)

An in vitro model of allergen-dependent IgE synthesis by human B lymphocytes: comparison of the response of an atopic and a non-atopic individual to Dermatophagoides spp. (house dust mite)

An allergen-dependent in vitro model of immunoglobulin E (IgE) synthesis by human B cells is reported. Using this model, it is demonstrated that polyclonal T cells and CD4+ Dermatophagoides spp. (house dust mite)-specific T-cell clones derived from an atopic, house dust mite (HDM)-allergic individual are able to support IgE synthesis by autologous B cells. The helper activity was interleukin-4 (IL-4) dependent as only cloned T cells expressing detectable mRNA for IL-4 were able to induce IgE synthesis without the addition of exogenous IL-4. Peripheral and cloned T cells reactive with HDM could also be identified from a non-atopic individual but neither population was able to support IgE production even in the presence of exogenous IL-4.

Induction of human IgE synthesis requires interleukin 4 and T/B cell interactions involving the T cell receptor/CD3 complex and MHC class II antigens

The induction of IgE synthesis by IL-4 requires T cells and monocytes, as well as T cell- and monocyte-derived cytokines. Optimal cytokine combinations, however, fail to induce highly purified B cells to secrete IgE, indicating that additional signals are required. We show herein that the induction of human IgE synthesis by rIL-4 requires cognate interaction between the T cell receptor/CD3 complex on T cells and MHC class II antigens on B cells: mAbs directed against these molecules completely blocked IL-4-dependent IgE induction. mAbs against cell adhesion molecules (CD2, CD4, LFA-1) also inhibited IgE synthesis induced by IL-4, confirming that cell-cell contact is necessary for IgE induction. The requirement for cognate T/B cell interaction was further shown by comparing the IgE-inducing ability of two human IL-4-producing alloreactive T cell clones: F6, which recognizes MHC class II antigens on both B cells and monocytes, and A1, which recognizes an HLA-DP-associated epitope expressed on monocytes, but not on B cells. When incubated with B cells and monocytes from a normal donor bearing the appropriate alloantigen, clone F6, but not clone A1, induced vigorous IgE synthesis, although both clones proliferated and secreted IL-4. Taken together, our results suggest that at least two, possibly synergizing, signals are required for the T cell-dependent induction of IgE synthesis by B cells: one signal is delivered by cognate T/B cell interaction, the other by T cell-derived IL-4.

Role of interleukins in induction and regulation of human IgE synthesis

Studies of human IgE synthesis are summarized and provide further insight into the cellular and molecular mechanisms involved in IgE regulation, as well as in the alterations responsible for IgE disregulation in some pathological conditions. These include the demonstration that IL-4 is the essential factor for the induction of human IgE syntheses. Another T cell-derived lymphokine, IFN-gamma negatively regulated the IgE synthesis induced by IL-4. These two lymphokines can be produced by different T helper cells, as shown in mice, but they can also be the product of the same T cells clones. Additional cellular and/or molecular signals appear to be involved in the IL-4-induced IgE synthesis, but their precise role in this process is undetermined. Finally, alternations of one or more of these regulatory mechanisms can be detected in patients with pathological conditions characterized by hyperproduction of IgE. In particular, the increased prevalence of T cells clones able to produce IL-4 appears to be a distinctive feature of patients with common atopy whereas a reduction in the proportion of IFN-gamma-producing T cells seems to be peculiar of both patients with hyper-IgE syndrome and patients with AIDS.

Regulation of human IgE synthesis

Allergic diseases result from the interaction with IgE bound to cell surface receptors. Therefore, rational therapeutic approaches to allergic diseases would be aimed at decreasing IgE and/or at blocking the binding of IgE to effector cells such as mast cells and monocytes. Our investigation of the mechanism of IgE synthesis in man shows that IgE synthesis by peripheral blood mononuclear cells (PBMC) absolutely requires the presence of IL-4 and requires endogenous IL-6, because antibody to IL-6 inhibits IgE production completely. IgE synthesis requires T/B cell contact and involves interactions between B cell surface MHC Class II molecules and T cell surface receptors, as antibodies to both of these cell surface molecules inhibit IgE synthesis. Furthermore, alloreactive T cell clones which are unable to engage the B cell MHC Class II molecules fail to induce IgE synthesis in spite of their ability to secrete IL-4. Studies on the immunoglobulin sites that are involved in IgE binding to high affinity receptors on mast cells and basophils have used recombinant fragments of IgE to block mast cell binding. These studies suggest that a stretch of 76 amino acids which straddles the C epsilon 2 and C epsilon 3 domains is essential for this binding. Parallel studies on IgE binding to low affinity receptors on monocytes and B cells suggest that sequences within C epsilon 3 are involved in this binding. Peptides or analogues that inhibit IgE binding to its cellular receptors may be useful in the treatment of allergic diseases.

Induction of interleukin-4-dependent IgE synthesis and interleukin-5-dependent eosinophil differentiation by supernatants of a human helper T-cell clone

The human alloreactive T-cell clone A1 produces interleukin (IL)-4, IL-5, and granulocyte macrophage-colony stimulating factor (GM-CSF), but not IL-2 or interferon-gamma (IFN-gamma), as assessed by probing for mRNA transcripts, immunoassays, or bioassays. Supernatants from clone A1 induced IgE synthesis by normal human peripheral blood mononuclear cells. IL-4 was shown to be necessary and sufficient for the induction of IgE by clone A1 supernatants. In contrast, IgE induction by clone A1 supernatants and recombinant (r) IL-4 was inhibited by IFN-gamma. This suggests that the absence of IFN-gamma from the IL-4-containing A1 supernatants was important for their IgE-inducing ability. Supernatants from clone A1 could also specifically induce the growth of cord blood cell progenitors and their differentiation into eosinophils but not into basophils. rIL-5, but not rIL-4 or rGM-CSF, also induced eosinophil maturation. These data suggest that IL-5 secreted by clone A1 was responsible for its ability to induce eosinophil differentiation. The implications of the concomitant production of IL-4 and IL-5 by a single T-cell clone are discussed.

Regulatory effects of human IgE-binding factors in the IgE synthesis by human and rat lymphocytes

We have previously established human T cell hybridomas which produce IgE-binding factors. Incubation of one of the T cell hybridomas, 166A2, with human IgE dimer in the presence of 1 microgram/ml bradykinin resulted in the formation of IgE-binding factors having affinity for lentil lectin. The factors selectively enhanced both IgE-forming cell responses of rat mesenteric lymph node (MLN) cells and spontaneous IgE synthesis by human peripheral blood B cells of atopic patients, without affecting the IgG response. The same factors that enhanced IgE synthesis of B cells from atopic patients also enhanced IgE synthesis induced under bystander conditions by activated alloreactive T cells. Fractionation of the affinity-purified IgE-binding factors by gel filtration revealed three molecular mass species, i.e., 60 kDa, 30 kDa and 15 kDa. The 60-kDa and 15-kDa IgE-binding factors selectively enhanced both the spontaneous IgE synthesis by B cells of atopic patients and IgE response of rat MLN cells. In contrast, the 30-kDa IgE-binding factors had only marginal enhancing effects on the IgE synthesis by both human B cells and rat MLN cells. When the 166A2 hybridoma cells were incubated with IgE dimer in the presence of glycosylation-inhibiting factor (GIF), essentially all IgE-binding factors formed by the cells had affinity for peanut agglutinin (PNA) but for neither lentil lectin nor concanavalin A. All of the 60-kDa, 30-kDa and 15-kDa species, having affinity for PNA, selectively suppressed the potentiating factor-enhanced IgE response of rat MLN cells. The factors also suppressed the IgE synthesis of human B cells from atopic patients when the synthesis was enhanced by IgE-potentiating factor. The results indicate that human IgE-binding factors regulate IgE synthesis by both human and rat lymphocytes.

IgE response and its regulation in allergic diseases

The distinguishing feature of the allergic person is his or her elevation of serum IgE. This propensity to develop a sustained IgE response is determined genetically. The biologic effects of IgE are mediated via Fc receptors (Fc epsilon R) present on mast cells and basophils (Fc epsilon R type 1) and subpopulations of monocytes, macrophages, eosinophils, and platelets (Fc epsilon R type 2). Interaction of allergen with IgE on these cells results in receptor "bridging" and the release of histamine and other inflammatory mediators. Fc epsilon R type 2 on lymphocytes and monocytes are upregulated in atopic disease and may play a role in the allergic inflammatory reaction. The activation of B cells to synthesize IgE requires several stages (see Fig. 2). T cells play an important role in the regulation of IgE synthesis. In vitro activation of resting B cells to synthesize IgE requires direct cellular interaction with T cells or the presence of IL4 for activation. The latter effect is inhibited by alpha-interferon. Preactivated B cells are influenced in an isotype-specific manner by T-cell-derived IgE binding factors (IgE-BF), which may act as IgE-potentiating or IgE-suppressive factors, depending on their degree of glycosylation. The regulation of IgE synthesis is an important area of investigation. It provides us with an understanding of the basis of the human allergic response and ultimately may provide the basis for novel strategies in the treatment of allergic diseases.

IgE production by normal human lymphocytes is induced by interleukin 4 and suppressed by interferons gamma and alpha and prostaglandin E2

The effect of human recombinant interleukin 4 (IL-4) on antibody production by normal peripheral blood mononuclear cells enriched for B cells was investigated. IL-4 preferentially induced IgE synthesis in vitro. In addition, a low induction of IgG production was observed, whereas IL-4 had no effect on IgA and IgM synthesis. The IL-4-induced IgE production by B cells required T cells and monocytes but was specifically inhibited by an anti-IL-4 antiserum indicating that, although IL-4 acts indirectly, it is responsible for the induction of IgE synthesis. IL-4-induced IgE production was blocked in a dose-dependent way by interferon gamma (IFN-gamma), interferon alpha (IFN-alpha), and prostaglandin E2. IFN-gamma also inhibited IL-4-induced IgG production. These inhibitory effects of IFN-gamma and IFN-alpha on IgE production cannot be attributed to toxic effects since IFN-alpha induced IgM production in the presence of IL-4, whereas IFN-gamma was ineffective in inhibiting IgG production induced by IL-2. IFN-gamma, IFN-alpha, and prostaglandin E2 also inhibited IL-4-induced expression of the low-affinity receptor for the Fc portion of IgE (CD23) on B cells, indicating that there is an association between CD23 expression and IL-4-induced IgE production. This theory was supported by the finding that IL-4-induced IgE production was inhibited by F(ab')2 fragments of an anti-CD23 monoclonal antibody.

T cell clones providing helper function for IgE synthesis release soluble factor(s) that induce IgE production in human B cells: possible role for interleukin 4 (IL-4)

We have previously demonstrated that a proportion of human T cell clones (TCC) derived from tonsil or peripheral blood (PB) of non-allergic donors, upon triggering with phytohaemagglutinin (PHA) or anti-CD3 monoclonal antibody (MoAb), were able to provide help for IgE synthesis in B cells from both allergic and non-allergic individuals. In this study we show that, upon PHA stimulation, culture supernatants from 10 selected TCC active on IgE synthesis also provided helper activity for IgE, whereas supernatants from unstimulated cultures of the same TCC were ineffective. In contrast, culture supernatants derived from five PHA-stimulated TCC, unable to provide helper function for IgE synthesis, consistently failed to elicit production of IgE. While the induction of IgE synthesis by TCC occurred in B cells from virtually all allergic and non-allergic donors, their soluble factor(s) were found to be able to provide substantial help for IgE production only in B cells from a proportion of donors tested. In addition, B cells from non-atopic donors usually appeared to be less responsive than atopic B cells to the activity of such factor(s). In contrast, synthesis of both IgG and IgM was induced in every B cell donor by both TCC and their supernatants. Partial characterization of the factor(s) providing helper function for IgE synthesis in B cells showed that it apparently had a mol. wt between 10 and 50 kD and did not bind to immobilized IgE. Such an activity appeared to be associated with the presence of interleukin 4 (IL-4) in supernatants and it was inhibited by adding both gamma-interferon and anti-human IL-4 antibody in culture.

Recognition by a human alloreactive T-cell clone of an HLA-DP-associated epitope on monocytes and fibroblasts but not on B cells

We examined the ability of a panel of allospecific (N = 9) and of TT-specific (N = 15) human inducer T-cell clones to respond to antigen presented by B cells or by monocytes. With one exception all T-cell clones responded equally well to antigen presented by monocytes, by lightly irradiated (1000 rads) peripheral blood resting B cells, or by heavily irradiated (7500 rads) Epstein-Barr virus (EBV)-transformed B cells. One alloreactive human T-cell clone, Clone A1, which recognized an HLA-DP-associated antigen proliferated in response to allogeneic monocytes and gamma-interferon-treated fibroblasts but not in response to allogeneic B cells even in the presence of autologous monocytes. Nonspecific conjugate formation between B cells and Clone A1 was normal. Yet in contrast to allogeneic monocytes, allogeneic B cells failed to induce a rise in the intracellular calcium ion concentration and failed to cause interleukin 2 (IL2) receptor expression in Clone A1. Neither interleukin 1 (IL1) nor phorbol myristate acetate (PMA) reversed the inability of Clone A1 to proliferate to allogeneic B cells. The failure of allogeneic B cells to stimulate A1 was not due to their lack of expression of the HLA-DP gene product recognized by Clone A1 or to excessive sialation of this product. These results suggest that Clone A1 recognizes an epitope associated with HLA-DP which is expressed on monocytes and on gamma-interferon-treated fibroblasts but which is either absent or altered on B cells.

Induction of human in vitro IgE synthesis via stimulation by anti-CD3 antibody

Mitogens such as pokeweed mitogen, Staphylococcus aureus Cowan I, concanavalin A and phytohemagglutinin and monoclonal anti-CD antibodies were examined for their capacity to induce IgE synthesis by peripheral blood leukocytes obtained from both atopic and nonatopic individuals. While lectins failed to induce IgE synthesis, monoclonal anti-CD3 antibodies were very potent stimuli for the induction of human in vitro IgE synthesis, possibly due to the activation of T cells. Activation via CD4 or CD8 molecules by OKT4 or OKT8 antibodies did not lead to a T cell-dependent modulation of IgE synthesis. PWM acted in synergy with the enhancing effect of anti-CD3 antibodies for IgE synthesis. In vitro IgG production was less affected. These results indicate that activation of T cell via CD3 molecules may be important in the regulation of IgE immune responses in man. Furthermore, the successful induction of IgE synthesis by anti-CD3 antibody in unfractionated peripheral blood leukocytes culture provides a simple model for investigation of human IgE regulatory mechanism in vitro.

Allergy in asthma. II. The highly atopic infant and chronic asthma

The relationship between allergy and asthma in infants and preschool children was investigated. One hundred nine children, median age 2 1/2 years, were examined immunologically by quantitation of serum IgE, RAST testing to 13 allergens, and culture of peripheral blood lymphocytes for spontaneous IgE formation. We examined a cross-section of infants and toddlers to determine whether the severity of asthma is associated with allergy as has been reported in older children with asthma. We identified a group of highly atopic infants and preschool children who have serum IgE at least 10 times the mean + 1 SE for age, multiple positive RASTs with early formation of IgE to inhalant antigens, and circulating B cells that spontaneously form IgE when these are cultured in vitro. Such highly atopic infants and preschool children were statistically more likely to have chronic asthma requiring multiple continuous medication compared to the rest of the population (p less than 0.01).

Role of interleukin-4 in the induction of human IgE synthesis and its suppression by interferon-gamma

Supernatants (SN) from 10 phytohemagglutinin (PHA)-stimulated human T cell clones (TCC), selected for their helper function on IgE synthesis, were found to provide IgE helper activity in atopic B cells showing low or undetectable spontaneous in vitro IgE synthesis. In contrast, SN from 5 PHA-stimulated TCC unable to provide helper function for IgE synthesis consistently failed to elicit IgE production. SN active on IgE synthesis contained high concentrations of interleukin-4 (IL-4), whereas inactive SN did not contain detectable amounts of IL-4. Moreover, the IgE helper activity of TCC SN was strongly inhibited by the addition of interferon-gamma (IFN-gamma) to B cell cultures. These data suggest that IL-4 may play a role in the induction of in vitro human IgE synthesis, whereas IFN-gamma displays an inhibitory effect.

Reversal of lymphocyte activation in vivo in the Kawasaki syndrome by intravenous gammaglobulin

The effect of intravenous gammaglobulin (IVGG) on the immunoregulatory abnormalities found during acute Kawasaki syndrome (KS) was studied in a randomized trial of IVGG plus aspirin (ASA) versus ASA alone. Before therapy, patients in each treatment group had increased numbers of circulating HLA-DR-bearing Leu 3+ helper T cells, a deficiency of Leu 2+ suppressor/cytotoxic T cells, and increased levels of spontaneous IgG and IgM synthesis by peripheral blood mononuclear cells. There were no significant differences (P greater than 0.1) between immunologic parameters measured on day 1 and day 4 in the ASA-treated group. In contrast, patients treated with ASA plus IVGG had by day 4 a highly significant decrease in HLA-Dr+ Leu 3+ helper T cells (P less than 0.001), an increase in Leu 2+ suppressor/cytotoxic T cells (P less than 0.01), and a decrease in spontaneous IgG (P less than 0.01) and IgM synthesis (P less than 0.001). These changes were associated with a reduction in the secretion of T cell-derived B cell helper factors (P less than 0.001). These findings indicate that treatment with IVGG suppresses the marked T and B cell activation found in patients with acute KS.