Analysis of changes in inter-cellular communications during Alzheimer's Disease pathogenesis reveals conserved changes in glutamatergic transmission in mice and humans

Analysis of system-wide cellular communication changes in Alzheimer's disease (AD) has recently been enabled by single nucleus RNA sequencing (snRNA-seq) and new computational methods. Here, we combined these to analyze data from postmortem human tissue from the entorhinal cortex of AD patients and compared our findings to those from multiomic data from the 5xFAD amyloidogenic mouse model at two different time points. Using the cellular communication inference tool CellChat we found that disease-related changes were largely related to neuronal excitability as well as synaptic communication, with specific signaling pathways including BMP, EGF, and EPHA, and relatively poor conservation of glial-related changes during disease. Further analysis using the neuron-specific NeuronChat revealed changes relating to metabotropic glutamate receptors as well as neuronal adhesion molecules including neurexins and neuroligins. Our results that cellular processes relating to excitotoxicity are the best conserved between 5xFAD mice and AD suggest that excitotoxicity is the main common feature between pathogenesis in 5xFAD mice and AD patients.

The role of skin tests with polyethylene glycol and polysorbate 80 in the vaccination campaign for COVID-19: results from an Italian multicenter survey

Summary

Background. International guidelines suggested skin tests with Polyethylene-glycol (PEG) and polysorbate 80 (PS-80), to investigate a possible hypersensitivity to these excipients either to identify subjects at risk of developing allergic reactions to Covid-19 vaccines, or in patients with suspected IgE mediated hypersensitivity reactions (HR) to the Covid-19 vaccine. The main purpose of this study was to investigate the prevalence of PEG and PS sensitization in patients with a clinical history of HR to drugs containing PEG/PS and in patients with a suspected Covid-19 vaccine immediate HR. Methods. This was a multicenter retrospective study conducted by allergists belonging to 20 Italian medical centers. Skin testing was performed in 531 patients with either a clinical history of suspected hypersensitivity reaction (HR) to drugs containing PEG and/or PS-80 (group 1:362 patient) or a suspected HR to Covid-19 vaccines (group 2: 169 patient), as suggested by the AAIITO/SIAAIC guidelines for the "management of patients at risk of allergic reactions to Covid-19 vaccines" [1]. Results. 10/362 (0.02%) had positive skin test to one or both excipients in group 1, 12/169 (7.1%) in group 2 (p less than 0.01). In group 2 HRs to Covid-19 vaccines were immediate in 10/12 of cases and anaphylaxis occurred in 4/12 of patients. Conclusions. The positivity of skin test with PEG and or PS before vaccination is extremely rare and mostly replaceable by an accurate clinical history. Sensitization to PEG and PS has to be investigated in patients with a previous immediate HR to a Covid-19 vaccine, in particular in patients with anaphylaxis.

Vespa velutina nigrithorax venom allergy: inhibition studies approach for the choice of specific immunotherapy

Summary

Vespa velutina nigrithorax (VVN), commonly known as Asian wasp because endemic in Asia, represents an alien species in Europe. VVN can induce allergic reactions similar to those caused by other Hymenoptera and deaths after VVN stings, presumably due to fatal allergic reactions, were reported. In the treatment of Hymenoptera venom hypersensitivity, specific immunotherapy (VIT) is highly effective, and the vaccine allergen-specificity plays a crucial role. Currently, there is no specific available VIT for VVN, so VVN stung patients with severe systemic reactions are treated with Vespula spp (Vspp) venom. It is also relevant to assess if patients stung by VVN and showing allergic reactions could be treated with the Hymenoptera commercially available extracts Vespa crabro (VC) and Vspp, or if they need the specific VIT with VVN venom extract. Our results suggested that both Vspp and VC venoms were able to inhibit the specific IgE for VVN, although the VC venom, compared to the venom of Vspp showed a higher inhibition.

An extended amygdala-midbrain circuit controlling cocaine withdrawal-induced anxiety and reinstatement

Although midbrain dopamine (DA) circuits are central to motivated behaviors, our knowledge of how experience modifies these circuits to facilitate subsequent behavioral adaptations is limited. Here we demonstrate the selective role of a ventral tegmental area DA projection to the amygdala (VTADA→amygdala) for cocaine-induced anxiety but not cocaine reward or sensitization. Our rabies virus-mediated circuit mapping approach reveals a persistent elevation in spontaneous and task-related activity of inhibitory GABAergic cells from the bed nucleus of the stria terminalis (BNST) and downstream VTADA→amygdala cells that can be detected even after a single cocaine exposure. Activity in BNSTGABA→midbrain cells is related to cocaine-induced anxiety but not reward or sensitization, and silencing this projection prevents development of anxiety during protracted withdrawal after cocaine administration. Finally, we observe that VTADA→amygdala cells are strongly activated after a challenge exposure to cocaine and that activity in these cells is necessary and sufficient for reinstatement of cocaine place preference.

A student-centered seminar course as a complementary approach to a traditional journal club

Graduate physiology programs strive to provide students with in-depth expertise in a particular academic discipline, often facilitating this process in the form of a departmental seminar course. Within the Department of Physiology and Biophysics at the University of California Irvine (UCI), students are required to attend a seminar course, most often designed as a journal club, each quarter until they are ready to graduate. While this format may work well in departments where research topics are closely related, it has historically been less successful in UCI's Department of Physiology and Biophysics, where wide-ranging interests make for little overlap in foundational knowledge, limiting meaningful engagement with the material or with peers in the class. In this paper, we describe a complementary approach of developing a syllabus around student interests and covering topics that are critical for student success but often omitted from graduate curricula, such as interview skills, grant writing, and scientific communication. Results from our preclass survey motivated this approach to the class, and our retrospective survey demonstrated the substantial differences in student engagement, enthusiasm, and perceived benefits of this course relative to the journal club style course. We hope that the success of our course may serve as an exemplar for strategies to engage students more effectively and provide critical training in diverse skillsets that will help students after graduation.

Uncovering the Connectivity Logic of the Ventral Tegmental Area

Decades of research have revealed the remarkable complexity of the midbrain dopamine (DA) system, which comprises cells principally located in the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). Neither homogenous nor serving a singular function, the midbrain DA system is instead composed of distinct cell populations that (1) receive different sets of inputs, (2) project to separate forebrain sites, and (3) are characterized by unique transcriptional and physiological signatures. To appreciate how these differences relate to circuit function, we first need to understand the anatomical connectivity of unique DA pathways and how this connectivity relates to DA-dependent motivated behavior. We and others have provided detailed maps of the input-output relationships of several subpopulations of midbrain DA cells and explored the roles of these different cell populations in directing behavioral output. In this study, we analyze VTA inputs and outputs as a high dimensional dataset (10 outputs, 22 inputs), deploying computational techniques well-suited to finding interpretable patterns in such data. In addition to reinforcing our previous conclusion that the connectivity in the VTA is dependent on spatial organization, our analysis also uncovered a set of inputs elevated onto each projection-defined VTADA cell type. For example, VTADA→NAcLat cells receive preferential innervation from inputs in the basal ganglia, while VTADA→Amygdala cells preferentially receive inputs from populations sending a distributed input across the VTA, which happen to be regions associated with the brain's stress circuitry. In addition, VTADA→NAcMed cells receive ventromedially biased inputs including from the preoptic area, ventral pallidum, and laterodorsal tegmentum, while VTADA→mPFC cells are defined by dominant inputs from the habenula and dorsal raphe. We also go on to show that the biased input logic to the VTADA cells can be recapitulated using projection architecture in the ventral midbrain, reinforcing our finding that most input differences identified using rabies-based (RABV) circuit mapping reflect projection archetypes within the VTA.

A connectomic analysis of deep brain stimulation for treatment-resistant depression

OBJECTIVE

Deep brain stimulation (DBS) has been used as a treatment of last resort for treatment-resistant depression (TRD) for more than a decade. Many DBS targets have been proposed and tested clinically, but the underlying circuit mechanisms remain unclear. Uncovering white matter tracts (WMT) activated by DBS targets may provide crucial information about the circuit substrates mediating DBS efficacy in ameliorating TRD.

METHODS

We performed probabilistic tractography using diffusion magnetic resonance imaging datas from 100 healthy volunteers in Human Connectome Project datasets to analyze the structural connectivity patterns of stimulation targeting currently-used DBS target for TRD. We generated mean and binary fiber distribution maps and calculated the numbers of WMT streamlines in the dataset.

RESULTS

Probabilistic tracking results revealed that activation of distinct DBS targets demonstrated modulation of overlapping but considerably distinct pathways. DBS targets were categorized into 4 groups: Cortical, Striatal, Thalamic, and Medial Forebrain Bundle according to their main modulated WMT and brain areas. Our data also revealed that Brodmann area 10 and amygdala are hub structures that are associated with all DBS targets.

CONCLUSIONS

Our results together suggest that the distinct mechanism of DBS targets implies individualized target selection and formulation in the future of DBS treatment for TRD. The modulation of Brodmann area 10 and amygdala may be critical for the efficacy of DBS-mediated treatment of TRD.

Allergic reactions after vaccination: translating guidelines into clinical practice

Summary

Vaccination represents one of the most powerful medical interventions on global health. Despite being safe, sustainable, and effective against infectious and in some cases also non-infectious diseases, it's nowadays facing general opinion's hesitancy because of a false perceived risk of adverse events. Adverse reactions to vaccines are relatively rare, instead, and those recognizing a hypersensitivity mechanism are even rarer. The purpose of this review is to offer a practical approach to adverse events after vaccination, focusing on immune-mediated reactions with particular regard to their recognition, diagnosis and management. According to clinical features, we propose an algorythm for allergologic work-up, which helps in confirming hypersensitivity to vaccine, nonetheless ensuring access to vaccination. Finally, a screening questionnaire is included, providing criteria for immunisation in specialized care settings.

Diminished Production of Interleukin 2 and Gamma-Interferon by Cloned «T» Cells from Patients with the Acquired Immunodeficiency Syndrome (AIDS)

A total of 76 T-cell clones established from peripheral blood (PB) of 2 patients with the acquired immune deficiency syndrome (AIDS) and of 141 T-cell clones established from PB of 3 normal donors were compared for their ability to produce interleukin 2 (IL-2) and gamma-interferon (γ-IFN). Twenty-seven clones from AIDS patients and 85 clones from controls expressed the CD4 phenotype, whereas 49 clones from AIDS patients and 56 clones from controls expressed the CD8 phenotype. There were no significant differences in the proportions of IL-2-producing CD4 T-cell clones established from PB of patients with AIDS and controls, but the mean concentration of IL-2 produced by CD4 clones from AIDS patients was significantly lower than that produced by CD4 clones from controls. Both the proportion of γ-IFN-producing CD4 clones and the mean concentration of γ-IFN produced by CD4 clones were significantly lower in AIDS patients than in controls. In contrast, there were no differences between AIDS patients and normal individuals in the proportion of IL-2- or Y-IFN-producing CD8 clones, or in the mean concentration of IL-2 and v-IFN produced by CD8 clones. These data suggest that the reduced ability of PB T-cells from patients with AIDS to produce IL-2 and v-IFN is not simply due to altered proportions or numbers of T-cell sub-populations, but also reflects intrinsic abnormalities of individual CD4 T lymphocytes.

Shrimp Allergy: Analysis of Commercially Available Extracts for In Vivo Diagnosis

BACKGROUND AND OBJECTIVE

Skin prick testing (SPT) with commercial extracts is the first step in the diagnosis of shrimp allergy, although its clinical efficiency is unknown. Objective: To analyze the clinical usefulness of all commercial crustacean extracts available for SPT in Italy.

METHODS

We performed a multicenter study of 157 shrimp-allergic patients who underwent SPT with 5 commercial crustacean extracts and with house dust mite (HDM) extract. Commercial extracts were analyzed using SDS-PAGE and compared with a freshly prepared in-house shrimp extract. IgE to Pen a 1/Pen m 1, Pen m 2, and Pen m 4 was determined, and immunoblot analysis was performed on a large number of sera.

RESULTS

The skin reactions caused by commercial crustacean extracts were extremely heterogeneous, resulting in 32 clinical profiles, with marked differences in protein content and missing proteins at molecular weights corresponding to those of major shrimp allergens. Only strong Pen a 1/Pen m 1 reactors reacted to both HDM and all 5 commercial extracts in SPT. Most patients, including those who were tropomyosin-negative, reacted to HDM. Patients reacted to a large and variable array of proteins, and IgE reactivity was common at high molecular weights (>50 kDa).

CONCLUSIONS

The in vivo diagnosis of shrimp allergy must continue to be based on SPT with fresh material. Shrimp-allergic patients frequently react to a number of ill-defined high-molecular-weight allergens, thus leaving currently available materials for component-resolved diagnosis largely insufficient. Mites and crustaceans probably share several allergens other than tropomyosin.

Heterogenity of IgE response to walnut and hazelnut in Italian allergic patients

BACKGROUND

The prevalence of IgE reactivity against genuine walnut and hazelnut allergens is poorly defined.

OBJECTIVE

The IgE response to walnut and hazelnut was investigated in Italian patients with primary allergy to these nuts.

METHODS

Sera from 36 patients allergic to hazelnut and/or walnut, not reactive to PR-10, profilin, and LTP, underwent immunoblot analysis with extracts of both nuts.

RESULTS

Most patients had a history of systemic symptoms following the ingestion of the offending food(s). Twelve patients were sensitized to both walnut and hazelnut, and 13 were sensitized to other nuts and seeds (cashew, peanut, sesame, pine nut, almond, Brazil nut, and pistachio). On walnut immunoblot, the 7 sera which scored positive showed much variability in their IgE profile. Two reacted uniquely at 10 kDa, and the others at 35 , 40, 45, 50, 67, and > 67 kDa. The profiles obtained under reducing and non-reducing conditions showed several differences. The 7 sera positive on hazelnut immunoblot under reducing conditions recognized sera at 10 kDa and at <10 kDa (n=1), 20 kDa (n=4), at about 22, 24, 30, 40, 43, 58, 60, and 90 kDa, and higher m.w. in other cases. Under non-reducing conditions IgE reactivity at 20, 28, 35, 40, 45, 60, 90, and 100 kDa, was detected. Only two sera scored positive under both conditions and showed an IgE profile that partly changed from one assay to another.

CONCLUSION

The current list of walnut and hazelnut allergens is far from being complete. Both reducing and non-reducing conditions are needed to detect IgE reactivity in individual patients.

Wellbeing, Illness Perception and Coping Strategies in Italian Celiac Patients

The clinical features of Celiac Disease (CD) are heterogeneous and both severity and extent of villous atrophy do not correlate with clinical presentation. This study aims to evaluate the psychological wellbeing of CD patients with a similar clinical pattern and to explore whether patients with different levels of wellbeing differed in illness perception and coping strategies. CD outpatients with proven diagnosis filled in validated questionnaires to investigate wellbeing (PGWBI), illness perception (IPQ-R) and coping style (COPE). One hundred and four patients underwent data analysis. Compared to Italian reference sample, CD patients reported a significantly reduced PGWBI total score (p<0.001), self-control (p<0.001), general health (p=0.002) and vitality (p<0.001) and increased anxiety (p=0.009). 7.7% of patients reported a positive wellbeing, 40.4% distress absence, 28.8% a moderate distress and 23.1% a severe distress. Patients with distress showed a different illness perception and reported more frequently two dysfunctional strategies: “focus on and venting emotions” (p= 0.009) and “substance abuse” (p= 0.01) compared to those having a positive wellbeing. A high percentage of CD patients experience distress and differ from those who reach wellbeing in illness perception and use of coping strategies. Assessing subjective viewpoint with standardized methods can provide useful information for a better management of CD patients.

Shrimp allergy in Italian adults: a multicenter study showing a high prevalence of sensitivity to novel high molecular weight allergens

BACKGROUND

Shrimp is a frequent cause of food allergy worldwide. Besides tropomyosin, several allergens have been described recently.

OBJECTIVE

We investigated which allergens are involved in Italian shrimp-allergic adults.

METHODS

Sera from 116 shrimp-allergic patients selected in 14 Italian allergy centers were studied. Skin prick tests with house dust mite (HDM) as well as measurements of IgE to Pen a 1 (shrimp tropomyosin) and whole shrimp extract were performed. All sera underwent shrimp immunoblot analysis, and inhibition experiments using HDM extract as inhibitor were carried out on some Pen a 1-negative sera.

RESULTS

Immunoblots showed much variability. IgE reactivity at about 30 kDa (tropomyosin) was found in <50% of cases, and reactivity at about 67 kDa and >90 kDa was frequent. Further reactivities at 14-18, 25, 43-50, about 60 and about 80 kDa were detected. Most subjects had a history of shrimp-induced systemic symptoms irrespective of the relevant allergen protein. IgE to Pen a 1 were detected in sera from 46 (41%) patients. Skin reactivity to HDM was found in 43/61 (70%) Pen 1-negative subjects and inhibition studies showed that pre-adsorption of sera with HDM extract induced a marked weakening of the signal at >67 kDa.

CONCLUSIONS

Several allergens other than tropomyosin are involved in shrimp allergy in adult Italian patients. Some hitherto not described high molecular weight allergens seem particularly relevant in this population and their cross-reactivity with HDM allergens makes them novel potential panallergens of invertebrates.

Cross reactivity between European hornet and yellow jacket venoms

BACKGROUND

Cross-reactions between venoms may be responsible for multiple diagnostic positivities in hymenoptera allergy. There is limited data on the cross-reactivity between Vespula spp and Vespa crabro, which is an important cause of severe reactions in some parts of Europe. We studied by CAP-inhibition assays and immunoblotting the cross-reactivity between the two venoms.

METHODS

Sera from patients with non discriminative skin/CAP positivity to both Vespula and Vespa crabro were collected for the analyses. Inhibition assays were carried out with a CAP method, incubating the sera separately with both venoms and subsequently measuring the specific IgE to venoms themselves. Immunoblotting was performed on sera with ambiguous results at the CAP-inhibition.

RESULTS

Seventeen patients had a severe reaction after Vespa crabro sting and proved skin and CAP positive also to vespula. In 11/17 patients, Vespula venom completely inhibited IgE binding to VC venom, whereas VC venom inhibited binding to Vespula venom only partially (<75%). In 6 subjects the CAP-inhibition provided inconclusive results and their sera were analysed by immunoblotting. The SDS-PAGE identified hyaluronidase, phospholipase A1 and antigen 5 as the main proteins of the venoms. In 5 sera the levels of IgE against antigen 5 of Vespa crabro were higher than IgE against Vespula germanica, thus indicating a true sensitisation to crabro.

CONCLUSION

In the case of multiple positivities to Vespa crabro and Vespula spp the CAP inhibition is helpful in detecting the cross-reactivities.

European Polistes venom allergy

The American Polistes species venom mixture--that of P. annularis, P. fuscatus, P. metricus and P. exclamans--was the only commercially available mixture for diagnosis and therapy until 1996. However, these species of Polistes are not present in Europe, where P. dominulus and P. gallicus and to a lesser extent P. nimphus are widespread. The aim of this study was to assess the allergenic differences among the commercial American mix, P. dominulus and P. gallicus venom in European patients and therefore to verify if this mixture is suitable for diagnosis in these patients. We carried out skin tests, radioallergosorbent tests (RAST) and RAST inhibition in Italian patients with adverse reactions to Polistes stings. RAST inhibition results demonstrated that cross-reactivity between the American and European species is only partial and that P. dominulus and P. gallicus venoms have exclusive allergens. Skin tests and direct RAST confirmed these results and also showed that European Polistes venom is more suitable than the American mix in Italian patients. Moreover, we found a high rate of cross-reactivity between P. dominulus and P. gallicus. To conclude, P. dominulus and/or P. gallicus venoms are necessary for diagnosis and therefore in the therapy of European patients.

Infiltrating cells and related cytokines in lesional skin of patients with chronic idiopathic urticaria and positive autologous serum skin test

In approximately one-third of patients with chronic idiopathic urticaria (CIU), autoantibodies against the high-affinity IgE receptor and/ or against IgE can be detected and a wheal-and-flare response can be provoked by the intradermal injection of autologous serum (ASST). In this study we aimed to further characterize the inflammatory response observed in the subgroup of CIU patients with positive ASST and serum-evoked histamine-release in vitro from basophils in comparison with unaffected skin and healthy donors. An immunohistochemical analysis of infiltrating cells (CD4, MPO, EG1, EG2, tryptase), cytokines (IL-4, IL-5, IFN-gamma), chemokines and chemokine receptors (IL-8, CCR3, CXCR3), and adhesion molecules (ICAM-1, VCAM-1, ELAM-1) was performed on seven selected patients (four males and three females; median age: 45 years; range: 22-57) and five healthy donors. Cytokine evaluation was also performed in five psoriatic patients to obtain an additional control. In spontaneous wheals we observed an increased number of CD4+ T lymphocytes when compared with the controls, and an increased number of neutrophils and eosinophils, whereas mast cells did not show a significant variation. A significant expression for IL-4 and IL-5 could only be observed in lesional skin, while IFN-gamma showed a slight expression in the same site. Chemokine receptors CCR3 and CXCR3 did not show a defined polarized response in either lesional or unaffected skin. An increased expression of all cellular adhesion molecules (CAMs) studied was detected in spontaneous wheals. The lack of a significant difference in the expression of tryptase + mast cells, T lymphocytes, IL-8, CXCR3 and CCR3, a few CAMs between the lesional and unaffected skin of CIU patients suggests a wide immunological activation that involves not only lesional tissues, but possibly extends to the whole of the skin's immune system.

Membrane tumour necrosis factor-alpha is involved in the polyclonal B-cell activation induced by HIV-infected human T cells

Infection of CD4+ T cells by human immune deficiency virus-1 (HIV-1) causes severe dysfunction of cellular immunity, but paradoxically results in intense polyclonal activation of B cells, possibly accounting for both hypergammaglobulinaemia and frequent development of B-cell malignancies seen in HIV-infected patients. We have reported that human CD4+ T-cell clones infected with HIV in vitro markedly stimulate immunoglobulin synthesis by B cells through a non-cognate, contact-dependent mechanism. We show here that HIV-infected T-cell clones do not express the CD40 ligand (CD40L), a molecule critical for non-cognate B-cell activation, but a small proportion of them do express membrane tumour-necrosis factor (TNF)-alpha. The ability of HIV-infected T-cell clones to induce polyclonal B-cell activation appears to be restricted to TNF-alpha-positive T blasts and is inhibited by antibodies against both TNF-alpha and TNF-alpha receptor. Freshly isolated CD4+ T cells from HIV-infected individuals express TNF-alpha on the cell membrane and induce TNF-alpha-mediated immunoglobulin production by B cells. Thus, membrane TNF-alpha seems to be involved in the polyclonal B-cell activation induced by HIV-infected T cells.

IL-4 and IFN (alpha and gamma) exert opposite regulatory effects on the development of cytolytic potential by Th1 or Th2 human T cell clones

The cytolytic potential of a total number of 118 CD4+ human T cell clones specific for purified protein derivative (PPD) from Mycobacterium tuberculosis, tetanus toxoid, Lolium perenne group I allergen (Lol p I), Poa pratensis group IX allergen (Poa p IX), or Toxocara canis excretory/secretory antigen(s) (TES) was assessed by both a lectin (PHA)-dependent and a MHC-restricted lytic assay and compared with their profile of cytokine secretion. The majority of clones with Th1 or Th0 cytokine profile exhibited cytolytic activity in both assays, whereas Th2 clones usually did not. There was an association between the cytolytic potential of T cell clones and their ability to produce IFN-gamma, even though IFN-gamma produced by T cell clones was not responsible for their cytolytic activity. IL-4 added in bulk culture before cloning inhibited not only the differentiation of PPD-specific T cells into Th1-like cell lines and clones, but also the development of their cytolytic potential. The depressive effect of IL-4 on the development of PPD-specific T cell lines with both Th1 cytokine profile and cytolytic potential was dependent on early addition of IL-4 in bulk cultures. In contrast, the addition in bulk culture of IFN-gamma enhanced both the cytolytic activity of PPD-specific T cell lines, as well as the proportion of PPD-specific T cell clones with cytolytic activity. The addition in bulk cultures before cloning of IFN-gamma or IFN-alpha favored the development of TES-specific and Poa p IX-specific T cells into T cell clones showing a Th0 or even a Th1, rather than a Th2, cytokine profile. Accordingly, most of TES- and Poa p IX-specific T cell clones derived from cultures containing IFN-gamma or IFN-alpha displayed strong cytolytic activity. These data indicate that the majority of human T cell clones that produce IFN-gamma, but not IL-4 (Th1-like), as well as of T cell clones that produce IFN-gamma in combination with IL-4 (Th0-like) are cytolytic. More importantly, they demonstrate that the addition of IFN (alpha and gamma) or IL-4 in bulk cultures before cloning may influence not only the cytokine profile of human CD4+ T cell clones but also their cytolytic potential.

IL-4 and IFN (alpha and gamma) exert opposite regulatory effects on the development of cytolytic potential by Th1 or Th2 human T cell clones

The cytolytic potential of a total number of 118 CD4+ human T cell clones specific for purified protein derivative (PPD) from Mycobacterium tuberculosis, tetanus toxoid, Lolium perenne group I allergen (Lol p I), Poa pratensis group IX allergen (Poa p IX), or Toxocara canis excretory/secretory antigen(s) (TES) was assessed by both a lectin (PHA)-dependent and a MHC-restricted lytic assay and compared with their profile of cytokine secretion. The majority of clones with Th1 or Th0 cytokine profile exhibited cytolytic activity in both assays, whereas Th2 clones usually did not. There was an association between the cytolytic potential of T cell clones and their ability to produce IFN-gamma, even though IFN-gamma produced by T cell clones was not responsible for their cytolytic activity. IL-4 added in bulk culture before cloning inhibited not only the differentiation of PPD-specific T cells into Th1-like cell lines and clones, but also the development of their cytolytic potential. The depressive effect of IL-4 on the development of PPD-specific T cell lines with both Th1 cytokine profile and cytolytic potential was dependent on early addition of IL-4 in bulk cultures. In contrast, the addition in bulk culture of IFN-gamma enhanced both the cytolytic activity of PPD-specific T cell lines, as well as the proportion of PPD-specific T cell clones with cytolytic activity. The addition in bulk cultures before cloning of IFN-gamma or IFN-alpha favored the development of TES-specific and Poa p IX-specific T cells into T cell clones showing a Th0 or even a Th1, rather than a Th2, cytokine profile. Accordingly, most of TES- and Poa p IX-specific T cell clones derived from cultures containing IFN-gamma or IFN-alpha displayed strong cytolytic activity. These data indicate that the majority of human T cell clones that produce IFN-gamma, but not IL-4 (Th1-like), as well as of T cell clones that produce IFN-gamma in combination with IL-4 (Th0-like) are cytolytic. More importantly, they demonstrate that the addition of IFN (alpha and gamma) or IL-4 in bulk cultures before cloning may influence not only the cytokine profile of human CD4+ T cell clones but also their cytolytic potential.

Aberrant interleukin (IL)-4 and IL-5 production in vitro by CD4+ helper T cells from atopic subjects

The cytokine secretion profiles of T cell lines (TCL) specific for purified protein derivative (PPD) or streptokinase (SK), contemporarily derived from nine atopic and nine nonatopic individuals, were compared. Upon stimulation with phorbol myristate acetate (PMA) plus anti-CD3 monoclonal antibody (mAb), all TCL from both atopics and nonatopics produced interleukin (IL)-2 and interferon (IFN)-gamma. The mean IL-2 production by PPD- or SK-specific TCL from both atopics and nonatopics was similar, whereas the mean IFN-gamma production by TCL derived from atopics was significantly lower. In addition, both PPD- and SK-specific TCL from atopics produced detectable amounts of IL-4 and IL-5, whereas the corresponding TCL derived from nonatopics did not. A total number of 107 and 99 PPD-specific CD4+ T cell clones (TCC) were then derived from TCL of 4 atopic and 4 nonatopic donors and assessed for their profile of cytokine production in response to stimulation with either PMA plus anti-CD3 mAb or the specific antigen. Under both these experimental conditions, virtually all PPD-specific TCC from both atopic and nonatopic individuals produced IL-2 and IFN-gamma. In contrast, the great majority of PPD-specific TCC derived from nonatopic individuals did not produce IL-4 and IL-5, whereas high proportions of PPD-specific TCC derived from atopic donors displayed the ability to produce noticeable amounts of IL-4 and IL-5 besides IL-2 and IFN-gamma. These data indicate that CD4+ T cells from atopic individuals are able to produce IL-4 and IL-5 in response to bacterial antigens, such as PPD and SK, that usually evoke responses with a restricted type-1 T helper (Th1)-like cytokine profile in nonatopic individuals. Aberrant IL-4 production by Th cells may represent one of the immune alterations responsible for enhanced IgE antibody production in atopic people.

Infection of peripheral mononuclear blood cells by hepatitis C virus

We investigated the infection of peripheral blood mononuclear cells (PBMNC) by hepatitis C virus (HCV) in 5 patients with HCV-related chronic hepatitis. The presence of HCV-RNA-positive and -negative strands was tested with the polymerase chain reaction (PCR) method. In all subjects, HCV-RNA was shown in PBMNC. In 3 cases, HCV-RNA was shown in the T- and B-cell populations, with viral RNA also present in the monocyte-macrophage fraction of two of these. HCV-RNA-negative stranded molecules, indicative of the viral multiplication, were significantly increased in cells maintained in cultures with PHA/PMA stimulation. The results indicate that HCV infect blood mononuclear cells, thus suggesting that this cellular tropism may play a role in HCV infection.

Human bone marrow non-B, non-T cells produce interleukin 4 in response to cross-linkage of Fc epsilon and Fc gamma receptors

Human bone marrow (BM) cells lacking T- and B-cell markers expressed RNA encoding interleukin (IL) 4 and secreted detectable amounts of IL-4 in supernatants in response to Fc epsilon or Fc gamma receptor (Fc epsilon R or Fc gamma R) cross-linking. In some experiments, IL-5 RNA expression in response to Fc epsilon R cross-linkage could also be detected. In contrast, RNA transcripts for, and secretion of, IL-2, IL-6, and interferon gamma were never observed. The presence of IL-3 in the cultures was essential for IL-4 production by non-B, non-T BM cells in response to Fc gamma R cross-linking and enhanced IL-4 RNA expression in response to Fc epsilon R cross-linking. Under the same experimental conditions, BM T and B lymphocytes, as well as peripheral blood T, B, and non-B, non-T cells, did not express IL-4 RNA. Prolonged incubation of non-B, non-T cells in IgE-free medium followed by extensive washing did not inhibit IL-4 production induced by anti-IgE antibodies, suggesting that the Fc epsilon R involved in the response has the characteristics of a high-affinity receptor. The Fc epsilon R+ cells were separated from the Fc epsilon R- cells by sorting non-B, non-T BM cell suspensions with fluorescein isothiocyanate-conjugated IgE and then assessed for both IL-4 RNA expression and alcian blue staining. Both IL-4-producing and alcian blue-positive cells segregated with the Fc epsilon R+ fraction. These data suggest that human BM cells, probably belonging to the mast cell and/or basophil lineage, are capable of producing IL-4 in response to Fc epsilon R or Fc gamma R cross-linkage.

Purified protein derivative of Mycobacterium tuberculosis and excretory-secretory antigen(s) of Toxocara canis expand in vitro human T cells with stable and opposite (type 1 T helper or type 2 T helper) profile of cytokine production

A large series of T cell clones (TCC) specific for purified protein derivative (PPD) of Mycobacterium tuberculosis (total 60) or Toxocara canis excretory/secretory (TES) antigen (total 69) were established from the peripheral blood of two healthy individuals and analyzed for their profile of cytokine production in response to stimulation with either the specific antigen or the polyclonal activator phorbol myristate acetate plus anti-CD3 antibody. Under both these experimental conditions, the great majority of PPD-specific TCC secreted IL-2 and IFN-gamma but not, or limited amounts of, IL-4 and IL-5. In contrast, most TES-specific TCC secreted IL-4 and IL-5 but not, or limited amounts of, IL-2 and IFN-gamma. PPD-specific TCC that failed to secrete IL-4 and IL-5, and TES-specific TCC that failed to secrete IL-2 and IFN-gamma, were found to lack transcripts for IL-4 and IL-5, or for IL-2 and IFN-gamma, respectively. During the course of the study, over a 6-mo period, the functional phenotype of both TES- and PPD-specific TCC was repeatedly assessed and remained constant. These data demonstrate that T cells with stable Th1 or Th2 functional pattern exist not only in mice but also in humans and suggest that in the course of natural immunization certain infectious agents preferentially expand T cell subsets with stable and definite profile of cytokine production.

In vitro infection with HIV enables human CD4+ T cell clones to induce noncognate contact-dependent polyclonal B cell activation

Eleven (nine CD4+ and two CD8+) protein purified derivative-specific and eight tetanus toxoid-specific T cell clones (TCC), established from the peripheral blood of healthy persons, were cocultured in vitro with irradiated mononuclear cells from patients infected by HIV in the presence of PHA and polybrene. Two weeks post-HIV exposure, all 17 CD4+, but neither of the two CD8+, TCC exhibited integration of HIV in their genoma, as detected by polymerase chain reaction analysis, and released HIV into their supernatants, as detected by measuring both reverse transcriptase activity and p24 Ag. When co-cultured with either autologous or allogeneic B cells, all CD4+ HIV-infected TCC induced the synthesis of extraordinarily high amounts of IgM, IgG, and IgA. In contrast, their noninfected counterparts could provide helper function for Ig synthesis by autologous B cells only in the presence of the specific Ag (or anti-CD3 antibody), and induced allogeneic B cells to synthesize Ig only upon stimulation with anti-CD3 antibody. The supernatants of HIV-infected TCC failed to stimulate Ig synthesis in B cells. More importantly, when HIV-infected clonal T blasts and B cells were cultured in different chambers separated by a millipore membrane, permeable to molecules but not to cells, Ig synthesis did not occur. The Ig synthesis induced by HIV-infected TCC was also markedly inhibited by the addition in culture of either anti-CD4 or anti-LFA-1 antibody. In contrast, HIV-infected TCC maintained their ability to provide helper function for Ig synthesis in the absence of any stimulus, even after fixation with p-formaldehyde. These data demonstrate that in vitro infection with HIV enables human T cells to stimulate Ig synthesis by B cells by an Ag-nonspecific, MHC-unrestricted, contact-dependent mechanism. This may explain, at least in part, the hypergammaglobulinemia and other phenomena related to polyclonal B cell activation frequently seen in HIV-infected persons.

In vitro infection with HIV enables human CD4+ T cell clones to induce noncognate contact-dependent polyclonal B cell activation

Eleven (nine CD4+ and two CD8+) protein purified derivative-specific and eight tetanus toxoid-specific T cell clones (TCC), established from the peripheral blood of healthy persons, were cocultured in vitro with irradiated mononuclear cells from patients infected by HIV in the presence of PHA and polybrene. Two weeks post-HIV exposure, all 17 CD4+, but neither of the two CD8+, TCC exhibited integration of HIV in their genoma, as detected by polymerase chain reaction analysis, and released HIV into their supernatants, as detected by measuring both reverse transcriptase activity and p24 Ag. When co-cultured with either autologous or allogeneic B cells, all CD4+ HIV-infected TCC induced the synthesis of extraordinarily high amounts of IgM, IgG, and IgA. In contrast, their noninfected counterparts could provide helper function for Ig synthesis by autologous B cells only in the presence of the specific Ag (or anti-CD3 antibody), and induced allogeneic B cells to synthesize Ig only upon stimulation with anti-CD3 antibody. The supernatants of HIV-infected TCC failed to stimulate Ig synthesis in B cells. More importantly, when HIV-infected clonal T blasts and B cells were cultured in different chambers separated by a millipore membrane, permeable to molecules but not to cells, Ig synthesis did not occur. The Ig synthesis induced by HIV-infected TCC was also markedly inhibited by the addition in culture of either anti-CD4 or anti-LFA-1 antibody. In contrast, HIV-infected TCC maintained their ability to provide helper function for Ig synthesis in the absence of any stimulus, even after fixation with p-formaldehyde. These data demonstrate that in vitro infection with HIV enables human T cells to stimulate Ig synthesis by B cells by an Ag-nonspecific, MHC-unrestricted, contact-dependent mechanism. This may explain, at least in part, the hypergammaglobulinemia and other phenomena related to polyclonal B cell activation frequently seen in HIV-infected persons.

Allergen- and bacterial antigen-specific T-cell clones established from atopic donors show a different profile of cytokine production

We have established a large panel of T-cell clones (TCCs) specific for Dermatophagoides pteronyssinus and Lolium perenne group I grass pollen allergens (total, 61) and for tetanus toxoid and protein purified derivative bacterial antigens (total, 38) from the peripheral blood of two atopic individuals and then analyzed their ability to produce interleukin 4 (IL-4), IL-5, and interferon gamma (IFN-gamma). Upon stimulation with phorbol 12-myristate 13-acetate plus anti-CD3 antibody, the great majority of TCCs specific for bacterial components was able to produce both IL-4 and IFN-gamma, whereas most D. pteronyssinus- and L. perenne group I-specific TCCs produced IL-4, but no, or limited, IFN-gamma. Moreover, the mean amounts of IL-4 and IFN-gamma released by allergen-specific TCCs were significantly higher and lower, respectively, than the mean amounts produced by TCCs specific for bacterial components. Under the same experimental conditions, virtually all allergen-specific TCCs, but only one-third of tested TCCs specific for bacterial components, expressed IL-5 RNA and secreted IL-5 in their supernatants. Eighteen TCCs (nine specific for allergens and nine specific for bacterial components) were also assessed for their ability to induce IgE synthesis by autologous B cells in response to stimulation with the specific antigen. Under these experimental conditions, all allergen-specific TCCs, but only one-third of TCCs specific for bacterial components that produced IL-4 but no, or little, IFN-gamma induced the synthesis of detectable amounts of IgE. The demonstration that most allergen-specific helper T cells in atopic individuals are able to produce high amounts of IL-4 (and IL-5), but no IFN-gamma, may explain why allergens induce production of IgE antibodies and increase eosinophils.

Accumulation of Th-2-like helper T cells in the conjunctiva of patients with vernal conjunctivitis

A total number of 132 T cell clones (TCC) were obtained by PHA-stimulation of single T cells from mononuclear cell suspensions of conjunctival flogistic infiltrates of three patients with vernal conjunctivitis (VC). The phenotype and functional properties of these TCC were compared with those of 122 TCC contemporarily established from PB mononuclear cell suspensions of the same patients, 120 TCC established from lymph nodes of three patients with nonspecific hyperplastic lymphoadenitis and 159 TCC established from thyroid lymphocyte infiltrates of three patients with Graves' disease. The great majority of conjunctival TCC displayed the CD4+ CD8- phenotype (CD4/CD8 ratios ranging from 6.1 to 7.0), whereas the mean CD4/CD8 ratios for control TCC ranged from 0.9 to 2.4. After stimulation with either PHA or PMA plus anti-CD3 mAb, conjunctival TCC differed from control TCC for their ability to produce cytokines. In particular, a large number of conjunctival TCC produced IL-4, but no, or limited amounts of, IFN-gamma, whereas no difference was observed between conjunctival and control TCC with regard to the production of IL-2. The failure of IFN-gamma production by conjunctival TCC was apparently not caused by delay or block in cytokine production, but actually reflected the lack of IFN-gamma transcription. Virtually all conjunctival TCC able to produce IL-4, but not IFN-gamma, as well as most of those producing both cytokines, provided helper function for IgE synthesis in allogeneic normal B cells. The accumulation in the conjunctiva of patients with vernal conjunctivitis of CD4+ T cells that, apart from the production of IL-2, resembles murine Th2 cells for their profile of cytokine production and helper function suggests a possible role for these cells in the pathogenesis of the disease.

Accumulation of Th-2-like helper T cells in the conjunctiva of patients with vernal conjunctivitis

A total number of 132 T cell clones (TCC) were obtained by PHA-stimulation of single T cells from mononuclear cell suspensions of conjunctival flogistic infiltrates of three patients with vernal conjunctivitis (VC). The phenotype and functional properties of these TCC were compared with those of 122 TCC contemporarily established from PB mononuclear cell suspensions of the same patients, 120 TCC established from lymph nodes of three patients with nonspecific hyperplastic lymphoadenitis and 159 TCC established from thyroid lymphocyte infiltrates of three patients with Graves' disease. The great majority of conjunctival TCC displayed the CD4+ CD8- phenotype (CD4/CD8 ratios ranging from 6.1 to 7.0), whereas the mean CD4/CD8 ratios for control TCC ranged from 0.9 to 2.4. After stimulation with either PHA or PMA plus anti-CD3 mAb, conjunctival TCC differed from control TCC for their ability to produce cytokines. In particular, a large number of conjunctival TCC produced IL-4, but no, or limited amounts of, IFN-gamma, whereas no difference was observed between conjunctival and control TCC with regard to the production of IL-2. The failure of IFN-gamma production by conjunctival TCC was apparently not caused by delay or block in cytokine production, but actually reflected the lack of IFN-gamma transcription. Virtually all conjunctival TCC able to produce IL-4, but not IFN-gamma, as well as most of those producing both cytokines, provided helper function for IgE synthesis in allogeneic normal B cells. The accumulation in the conjunctiva of patients with vernal conjunctivitis of CD4+ T cells that, apart from the production of IL-2, resembles murine Th2 cells for their profile of cytokine production and helper function suggests a possible role for these cells in the pathogenesis of the disease.

In vitro infection with HIV of antigen-specific T cell clones derived from HIV-seronegative individuals. Effects on cytokine production and helper function

Three human T cell clones (TCC) specific for purified protein derivative of Mycobacterium tuberculosis were incubated in the presence of polybrene and phytohemagglutinin with irradiated mononuclear cells from one individual exhibiting seropositivity for human immunodeficiency virus (HIV) and high levels of circulating p24 antigen. After three weeks, TCC showed HIV integration in their DNA, as shown by polymerase chain reaction analysis and Southern blot technique. All the three HIV-infected TCC maintained their ability to recognize the specific antigen, even if their proliferative ability was reduced. The ability of the HIV-infected TCC to produce IL-2, IL-4 and IFN-gamma in response to phorbol myristate acetate plus anti-CD3 monoclonal antibody was decreased, whereas their ability to produce TNF-alpha was unaffected or even enhanced. Two out of the three HIV-infected TCC showed the ability to provide helper function for polyclonal immunoglobulin production when cocultured with autologous B cells in the absence of any stimulant. These data suggest that in vitro infection of normal human TCC may provide a useful model for the study of immunological alterations induced by HIV.

Increased numbers of Th2-like CD4+ T cells in target organs and in the allergen-specific repertoire of allergic patients. Possible role of IL-4 produced by non-T cells

Phytohemagglutinin (PHA)-induced human T cell clones (TCC) derived from conjunctival flogistic tissues of 3 patients with vernal conjunctivitis produced unusually high amounts of interleukin-4 (IL-4) and no, or limited amounts of, gamma-interferon (IFN-gamma). Allergen (Dermatophagoides pteronyssinus or Lolium perenne group I)-specific TCC derived from peripheral blood of two atopic donors produced significantly higher amounts of IL-4 and significantly lower amounts of IFN-gamma than TCC specific for bacterial antigens (tetanus toxoid and PPD) contemporarily established from the same donors. These data provide evidence for a compartimentalization of Th2-like helper T cells in target organs and in the allergen-specific T cell repertoire of allergic patients. Non-B, non-T bone marrow cells could produce IL-4, but not IL-2 or IFN-gamma, in response to cross-linkage of Fc epsilon type I receptors. These cells may further contribute to the maintenance and amplification of allergic inflammation.

Noncognate contact-dependent B cell activation can promote IL-4-dependent in vitro human IgE synthesis

We have previously shown that IL-4 is an essential mediator for the synthesis of human IgE in vitro. In this study we demonstrate that prior physical contact with T cells is required by B cells to synthesize IgE in response to IL-4. Both autologous and allogeneic freshly prepared T cells were consistently able to support IL-4-dependent IgE synthesis, provided that they were added to B cells together with, or before, the addition of IL-4. In addition, most CD4+, as well as a proportion of CD8+, PHA-induced T cell clones (TCC) established from two HLA-DR incompatible donors, supported, in the presence of exogenous IL-4, the synthesis of IgE in B cells from the majority of individuals tested including both donors of cloned T cells. An alloreactive TCC able to produce IL-4 in response to HLA-DR4+ B cells and to induce HLA-DR4+ B cells to synthesize IgE, acquired the ability to support IgE synthesis by B cells lacking the appropriate alloantigen provided that exogenous IL-4 was added. Although the ability of freshly prepared T cells to support IgE synthesis was consistently abrogated by fixation with paraformaldehyde (PF), such a treatment variably affected the IgE-inducing ability of TCC. Preactivation with anti-CD3 before treatment with PF maintained or even enhanced the ability of TCC to support IL-4-dependent IgE synthesis. More importantly, preactivation with anti-CD3, followed by fixation with PF, enabled TCC, apparently devoid of IgE-inducing activity in unfixed condition, to support IL-4-dependent IgE synthesis. Taken together these data suggest that at least two signals are involved in the triggering of human B cells to IgE production: the first is delivered by a T-B cell contact and the second by IL-4. The physical signal delivered by T cells does not necessarily consist of cognate interaction. Non-cognate contact-dependent induction of B cells to IgE synthesis in response to IL-4 appears to be related to molecule(s) distinct from the TCR/CD3 complex, but fully expressed on the membrane of TCR/CD3-activated T cells.

Noncognate contact-dependent B cell activation can promote IL-4-dependent in vitro human IgE synthesis

We have previously shown that IL-4 is an essential mediator for the synthesis of human IgE in vitro. In this study we demonstrate that prior physical contact with T cells is required by B cells to synthesize IgE in response to IL-4. Both autologous and allogeneic freshly prepared T cells were consistently able to support IL-4-dependent IgE synthesis, provided that they were added to B cells together with, or before, the addition of IL-4. In addition, most CD4+, as well as a proportion of CD8+, PHA-induced T cell clones (TCC) established from two HLA-DR incompatible donors, supported, in the presence of exogenous IL-4, the synthesis of IgE in B cells from the majority of individuals tested including both donors of cloned T cells. An alloreactive TCC able to produce IL-4 in response to HLA-DR4+ B cells and to induce HLA-DR4+ B cells to synthesize IgE, acquired the ability to support IgE synthesis by B cells lacking the appropriate alloantigen provided that exogenous IL-4 was added. Although the ability of freshly prepared T cells to support IgE synthesis was consistently abrogated by fixation with paraformaldehyde (PF), such a treatment variably affected the IgE-inducing ability of TCC. Preactivation with anti-CD3 before treatment with PF maintained or even enhanced the ability of TCC to support IL-4-dependent IgE synthesis. More importantly, preactivation with anti-CD3, followed by fixation with PF, enabled TCC, apparently devoid of IgE-inducing activity in unfixed condition, to support IL-4-dependent IgE synthesis. Taken together these data suggest that at least two signals are involved in the triggering of human B cells to IgE production: the first is delivered by a T-B cell contact and the second by IL-4. The physical signal delivered by T cells does not necessarily consist of cognate interaction. Non-cognate contact-dependent induction of B cells to IgE synthesis in response to IL-4 appears to be related to molecule(s) distinct from the TCR/CD3 complex, but fully expressed on the membrane of TCR/CD3-activated T cells.

Defective in vitro production of gamma-interferon and tumor necrosis factor-alpha by circulating T cells from patients with the hyper-immunoglobulin E syndrome

Circulating T cells from four patients with the hyper-IgE syndrome were found to produce significantly lower concentrations of interferon-gamma (IFN-gamma) in response to stimulation with phytohemagglutinin (PHA) than did T cells from eight age-matched healthy controls, three patients with atopic dermatitis and one patient with chronic granulomatous disease. A clonal analysis revealed that patients with hyper-IgE syndrome had markedly lower proportions of circulating T cells able to produce IFN-gamma and tumor necrosis factor-alpha (TNF-alpha) in comparison with controls. In contrast, the proportions of peripheral blood T cells able to produce IL-4 or IL-2 were not significantly different in patients and controls. All the four patients with hyper-IgE syndrome showed high proportions of circulating CD4+ helper T cells able to induce IgE synthesis in allogeneic B cells, as well. Such an activity for IgE synthesis appeared to be positively correlated with IL-4 production by T cells and inversely related to the ability of the same T cells to produce IFN-gamma. Since IFN-gamma exerts an inhibitory effect on the synthesis of IgE and both IFN-gamma and TNF-alpha play an important role in inflammatory reactions, we suggest that the defective production of IFN-gamma may be responsible for hyperproduction of IgE and the combined defect of IFN-gamma and TNF-alpha may contribute to the undue susceptibility to infections seen in patients with hyper-IgE syndrome.

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.

Role of interleukins in induction and regulation of human IgE

The studies on human IgE synthesis here summarized 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. They have clearly demonstrated that IL-4 is the essential factor for the induction of human IgE synthesis, since no substantial IgE production in vitro could be obtained in the absence of this lymphokine. Another T cell-derived lymphokine, IFN gamma, negatively regulates 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 cell clones. In such a case, the possibility that a given clone provides helper function for IgE seems to be dependent on the balance between the amounts of the two lymphokines produced. The IgE helper activity of rIL-4 appeared to be dependent on the presence in culture of appropriate concentrations of T lymphocytes, suggesting that T-B cell contact or other interleukins, such as IL-2 and IL-6, are needed in IL-4-dependent IgE synthesis. Finally, alterations of one or more of these regulatory mechanisms may play a crucial role in the pathogenesis of diseases characterized by a hyperproduction of IgE.

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.

Role of interleukin 4 and gamma interferon in the regulation of human IgE synthesis: possible alterations in atopic patients

The IgE helper function of human T cell clones or their phytohemagglutinin-induced supernatants was positively correlated with their ability to produce or their content in interleukin 4 (IL-4), whereas it was inversely correlated with production of or content in gamma interferon. The addition to B cell cultures of anti-IL-4 antibody abolished not only the IgE synthesis induced by recombinant human IL-4, but also that induced by IL-4-producing T cell clones or their phytohemagglutinin-induced supernatants. A clonal analysis in nonatopic donors and patients with common atopy showed that atopics possess in their peripheral blood significantly higher numbers of T cells able to secrete IL-4 and to provide helper function for IgE.