Donatella Macchia

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.

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.

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 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.

Human TH1 and TH2 Subsets

Human CD4+ T cell clones secreting different patterns of cytokines similar to TH1 and TH2 cells described in mice have been demonstrated. These human TH1 and TH2 clones are produced in response to different antigens and exhibit distinct functional properties. TH1 clones are produced in response to intracellular bacteria and viruses, do not provide help for IgE production and possess cytolytic potential, whereas TH2 clones are produced in response to allergens and helminth components, provide optimal help for IgM, IgG, IgA and IgE synthesis, and lack cytolytic potential. The cytokine profile of ‘natural’ immunity evoked by intracellular parasites and viruses through the activation of macrophages and NK cells probably determines the phenotype of the subsequent specific immune (TH1) response. TH1 cells are not only involved in the protection against intracellular parasites but also play a role in the genesis of some organ-specific autoimmune diseases, such as Hashimoto’s thyroiditis. In contrast, TH2 cells are responsible for the initiation of the allergic cascade.

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.

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.

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.

Role of T Cells in the Pathogenesis of Hodgkin's Disease

Publisher Summary Despite the great progress that has been achieved in recent years in the diagnosis and treatment of Hodgkins lymphoma, the etiopathogenesis of this disease still remains obscure. Definite proof that Hodgkins disease (HD) is a malignant neoplasm, albeit a remarkably atypical one, has been provided during the past two decades by a number of cytogenetic, immunological, and molecular biology studies. Several fundamental issues, however, still remain open. They include the genesis of the immune deficiency, the nature of the normal counterpart of the neoplastic cells, and the role of other tumor-infiltrating lymphocytes. This chapter describes the immunological alterations found in untreated HD patients, mainly focusing on those involving the T and B cell compartments. The chapter also discusses the hypotheses on the origin of Reed–Sternberg (RS) cells and describes the role of the cells surrounding them in involved lymphoid organs.

The IgE response in atopy and infections

The IgE antibody system represents an important defense mechanism against offending agents coming from the respiratory and gastrointestinal tracts. The human pathological condition most commonly associated with hyperproduction of IgE is atopy, the familial allergic disorder of immediate-type hypersensitivity to environmental allergens. Dysregulation of IgE synthesis has also been observed in clinical disorders often associated with immunodeficiency and/or infections, such as the Hyper-lgE syndromes (1), parasitic infestations, some primary and secondary immunodeficiencies (2, 3), AIDS (4), the acute phase of GVHD (5). Therefore, the understanding of mechanisms involved in IgE regulation is of primary importance in order to define the alterations responsible for allergic diseases, as well as other pathological conditions characterized by hyperproduction of IgE. In the first part of this paper we have summarized the mechanisms that regulate the synthesis of IgE in humans. In the second part, we discuss the pathophysiological aspects of IgE dysregulation in disorders characterized by hyperproduction of IgE.