Interleukins, from 1 to 37, and interferon-γ: receptors, functions, and roles in diseases.

Advancing our understanding of mechanisms of immune regulation in allergy, asthma, autoimmune diseases, tumor development, organ transplantation, and chronic infections could lead to effective and targeted therapies. Subsets of immune and inflammatory cells interact via ILs and IFNs; reciprocal regulation and counter balance among T(h) and regulatory T cells, as well as subsets of B cells, offer opportunities for immune interventions. Here, we review current knowledge about ILs 1 to 37 and IFN-γ. Our understanding of the effects of ILs has greatly increased since the discoveries of monocyte IL (called IL-1) and lymphocyte IL (called IL-2); more than 40 cytokines are now designated as ILs. Studies of transgenic or knockout mice with altered expression of these cytokines or their receptors and analyses of mutations and polymorphisms in human genes that encode these products have provided important information about IL and IFN functions. We discuss their signaling pathways, cellular sources, targets, roles in immune regulation and cellular networks, roles in allergy and asthma, and roles in defense against infections.

HIV interferes with SOCS-1 and -3 expression levels driving immune activation.

HIV infection is characterized by sustained immune activation, which is reflected by activated T cells and, in particular, by increased levels of phosphorylated STAT proteins. Here, we hypothesized that T-cell activation in HIV infection is partially due to the inability of SOCS-1 and SOCS-3 to control the JAK/STAT pathway. We found higher levels of SOCS-1/3 mRNA levels in CD4(+) T cells of HIV-infected patients than in healthy controls. However, SOCS protein levels were lower, explaining the lack of attenuation of the JAK/STAT pathway. Infection of CD4(+) T cells alone did not activate STATs, while ex vivo infection of PBMC did, indicating that non-T cells critical for shaping the immune response, e.g. DC were responsible for the STAT-1 activation. Supernatants from ex vivo-infected PBMC transferred to CD4(+) T cells induced JAK/STAT activation, pointing to a central role of soluble factors. Notably, over-expression of SOCS-1/3 in CD4(+) T cells prevented JAK/STAT activation. Thus, HIV infection interferes with SOCS-1/3 expression driving immune activation. Sustained immune activation disrupts the lymphoid system and favors HIV replication since HIV preferentially infects activated cells. We speculate that regulating SOCS may be a potential way to counteract immune activation in HIV disease.

Chlamydia pneumoniae-induced memory CD4+ T-cell activation in human peripheral blood correlates with distinct antibody response patterns.

Chlamydia pneumoniae is a frequent pathogen of the respiratory tract, and persistent infections with this obligate intracellular bacterium have been associated with different severe sequelae. Although T-cell activation during acute C. pneumoniae infections has been described, little is known about the frequency or the role of the C. pneumoniae-specific memory T cells that reside in the human body after the resolution of the infection. In the present study, the C. pneumoniae-induced T-cell responses in peripheral blood mononuclear cells of 56 healthy volunteers were analyzed and compared to the donor's serum antibody reactivity toward whole C. pneumoniae as well as recombinant C. pneumoniae antigens. Following short-term stimulation with C. pneumoniae, both gamma interferon (IFN-gamma)- and interleukin-2 (IL-2)-producing CD4(+) T-cell responses could be detected in 16 of 56 healthy individuals. C. pneumoniae-activated CD4(+) T cells expressed CD154, a marker for T-cell receptor-dependent activation, and displayed a phenotype of central memory T cells showing dominant IL-2 production but also IFN-gamma production. Interestingly, individuals with both IFN-gamma- and IL-2-producing responses showed significantly decreased immunoglobulin G reactivity toward C. pneumoniae RpoA and DnaK, antigens known to be strongly upregulated during chlamydial persistence, compared to IgG reactivity of seropositive individuals with no T-cell response or CD4(+) T-cell responses involving the production of a single cytokine (IFN-gamma or IL-2). Our results demonstrate that memory CD4(+) T cells responding to C. pneumoniae stimulation can be detected in the circulation of healthy donors. Furthermore, among seropositive individuals, the presence or the absence of dual IFN-gamma- and IL-2-producing T-cell responses was associated with distinct patterns of antibody responses toward persistence-associated C. pneumoniae antigens.

Exploring the repertoire of IgE-binding self-antigens associated with atopic eczema.

BACKGROUND: Atopic eczema (AE) is the most common chronic inflammatory skin disease. Recent data demonstrate the presence of autoreactive serum IgE antibodies correlating with the severity of the disease. OBJECTIVE: Although several IgE-binding self-antigens have been reported, the whole repertoire of IgE-binding self-antigens is unknown. We aimed to estimate the repertoire size of autoreactive proteins related to AE and clone, produce, and characterize humoral and T-cell responses against novel self-antigens. METHODS: Phage surface-displayed human cDNA libraries were enriched for clones binding to serum IgE from patients with AE and screened by using high-throughput technology. Selected clones were used to produce the encoded proteins, to test their IgE-binding ability in Western blots and ELISAs, and their ability to induce mediator release from basophils of sensitized individuals. RESULTS: One hundred forty sequences encoding potential IgE-binding self-antigens associated with AE were identified. Sixteen sequences encoded already described self-antigens. Three new sequences showed homology with environmental allergens, 86 encoded known human proteins, 7 predicted proteins, and 28 showed sequence identity with genomic contigs. Immunoblotting and ELISA experiments demonstrated the presence of IgE antibodies in sera from patients with AE to 5 selected recombinant self-antigens and their ability to induce mediator release from basophils of patients with AE who have self-antigen-specific IgE antibodies. CONCLUSION: These data demonstrate a broad spectrum of at least 140 IgE-binding self-antigens associated with AE. By binding IgE antibodies or activating specific T cells, they might promote, perpetuate, or both existing skin inflammation.

Cross-reactivity among fungal allergens: a clinically relevant phenomenon?

Atopic patients suffering from allergic asthma, allergic rhinitis, or atopic eczema often have detectable levels of serum IgE antibodies to fungi. Although the association between fungal sensitisation and different forms of allergic diseases, including allergic asthma and life-threatening allergic bronchopulmonary aspergillosis, is well established, the clinical relevance of cross-reactivity among different fungal species remains largely unknown. Recent progress in molecular cloning of fungal allergens and the availability of more than 40 completely sequenced fungal genomes facilitates characterisation, cloning, and production of highly pure recombinant allergens, identification of homologous and orthologous allergens widespread among the fungal kingdom, in silico prediction, and experimental in vitro and in vivo verification of cross-reactivity between homologous pan-allergens. These studies indicate that cross-reactivity is an important component of fungal sensitisation.

Immunoglobulin-E-mediated reactivity to self antigens: a controversial issue.

Immunoglobulin E (IgE) reactivity to self antigens is well established in vitro by ELISA, inhibition ELISA, Western blot analyses and T cell proliferation experiments. In vivo, IgE-binding self antigens are able to elicit strong type I reactions in sensitized individuals and, in the case of human manganese superoxide dismutase, to elicit eczematous reactions on healthy skin areas of patients suffering from atopic eczema. The reactions against self antigens sharing structural homology with environmental allergens can be plausibly explained by molecular mimicry between common B cell epitopes. For the second class of IgE-binding self antigens without sequence homology to known allergens, it is still unclear if the structures are able to induce a B cell switch to IgE production, or if the reactivity is due to sequence similarity shared with not yet detected environmental allergens. However, in all cases, cross-reactivity is never complete, indicating either a lower affinity of IgE antibodies to self allergens than to the homologous environmental allergens or the presence of additional B cell epitopes on the surface of the environmental allergens, or both. Increasing evidence shows that self allergens could play a decisive role in the exacerbation of long-lasting atopic diseases. However, the only observation supporting a clinical role of IgE-mediated autoreactivity is confined to the fact that IgE levels against self antigens correlate with disease severity.

Cross-reactivity and 1.4-A crystal structure of Malassezia sympodialis thioredoxin (Mala s 13), a member of a new pan-allergen family.

We have identified thioredoxins (Trx) of Malassezia sympodialis, a yeast involved in the pathogenesis of atopic eczema, and of Aspergillus fumigatus, a fungus involved in pulmonary complications, as novel IgE-binding proteins. We show that these Trx, including the human enzyme, represent cross-reactive structures recognized by serum IgE from individuals sensitized to M. sympodialis Trx. Moreover, all three proteins were able to elicit immediate-type allergic skin reactions in sensitized individuals, indicating a humoral immune response based on molecular mimicry. To analyze structural elements involved in these reactions, the three-dimensional structure of M. sympodialis Trx (Mala s 13) has been determined at 1.4-A resolution by x-ray diffraction analysis. The structure was solved by molecular replacement and refined to a crystallographic R factor of 14.0% and a free R factor of 16.8% and shows the typical Trx fold. Mala s 13 shares 45% sequence identity with human Trx and superposition of the solved Mala s 13 structure with those of human Trx reveals a high similarity with a root mean square deviation of 1.11 A for all Calpha atoms. In a detailed analysis of the molecular surface in combination with sequence alignment, we identified conserved solvent-exposed amino acids scattered over the surface in both structures which cluster to patches, thus forming putative conformational B cell epitopes potentially involved in IgE-mediated cross- and autoreactivity.

Critical evaluation of urine-based PCR assay for diagnosis of Lyme borreliosis.

Many approaches were made in recent years to establish urine PCR as a diagnostic tool for Lyme borreliosis, but results are contradictory. In the present study, a standardized protocol spiking urine from healthy donors with a defined amount of whole Borrelia or Borrelia DNA was established. The development of a nested real-time PCR targeting ospA enabled a highly sensitive and quantitative analysis of these samples. We show the following. (i) Storage of spiked urine samples for up to 6 months at--20 degrees C had no negative effect on spike recovery. (ii) Centrifugation of 10 ml of urine at 40,000 x g for 30 min resulted in a concentration of both spikes, i.e., whole Borrelia and DNA. (iii) The inhibition of DNA spike recovery in 48% (11 of 23 samples) of urine samples tested could be attributed to nuclease activity. This was abrogated by alkalizing the urine or by working with the samples on ice. Despite optimized conditions, analysis of urine samples of 12 patients with erythema migrans, the clinical stage considered to be associated with the highest bacterial load, revealed a positive result in only one sample. All 12 samples were negative by an alternative PCR targeting flagellin. The results of our study support doubts that urine is a suitable material for diagnosis of Lyme borreliosis.