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Notes: The concept that activation of MHC class I-restricted CD8+ cells entirely depends on help from MHC class II-restricted CD4+ T cells has recently been supplemented with an alternative model in which CD8+ cells can directly be activated by MHC class I-expressing professional antigen-presenting cells (APC), which are able to deliver an accessory signal. The authors analysed the role of CD28-mediated costimulation for T helper cell-independent activation of purified human CD8+ T cells in two different in vitro models. Freshly isolated CD8+ cells could be activated (proliferation, IL-2 production and cytotoxic activity) by anti-CD3-presenting FcγR+ mouse cells transfected with the human CD28 ligand, CD80, as the only accessory signal. On the other hand, activation of CD8+ cells by allogeneic MHC class I on EBV-transformed B cells, which express two different CD28 ligands, CD80 and CD86, also proceeded very efficiently (proliferation, cytotoxic activity and CD25 expression), but was either not, or only partially, blocked by anti-CD80 and anti-CD86 MoAb or CTLA-4Ig. This indicates that other costimulatory signals are also effective, and that CD28 triggering is not absolutely required for initial T-cell activation. CsA and CD80/CD86-blocking agents were synergistic in completely inhibiting activation of CD8+ cells in the MLR with allogeneic B-cell lines. This combination also induced non-responsiveness of CD8+ cells upon restimulation in the absence of blocking agents. Therefore, although professional APC can apparently provide multiple costimulatory signals for direct activation of CD8+ T cells, the signal derived from CD80/CD86 is unique in providing CsA-resistance.

Notes: The ligation between Leucocyte-Function-Associated Molecule I (LFA-1) and Intercellular Adhesion Molecules (ICAM) is thought to be an important component in the stimulatory interaction between antigen-presenting cells (APC) and T cells. Similar to antigenic stimulation, T-cell stimulation with pokeweed mitogen (PWM) is highly dependent on monocytes as accessory cells. This is partly a consequence of the requirement for mitogen presentation by the monocytes. The study described here addressed the question of whether LFA-1 ligation by accessory cells influences the activation of T cells with PWM. To avoid multiple costimulatory interactions between T cells and monocytes. experiments were performed with purified T cells, which were stimulated with PWM bound on autologous red blood cells (PWM-RBC). Binding on the RBC substituted partly for PWM presentation by the monocytes. Anti-LFA-1 MoAbs were presented in the immobilized form in order to mimick LFA-1 ligation by cell-bound ICAM. Three out of three different MoAbs against the β-chain of the LFA-1 molecule (CD18) and two out of three MoAbs against the α-chain (CD11a) had an enhancing effect on T-cell proliferation, Proliferation was increased further by simultaneous addition of interleukin (IL)-1 β and IL-6. Ligation of the LFA-1 molecule was found to enhance IL-2 production and tumour necrosis faclor-α (TNF-α) production. The results suggest that interaction of LFA-1 with ICAM on the monocytes contributes to the accessory signal activity of monocytes in T-cell activation with PWM.

Notes: Interleukin (IL)-10, an immunomodulatory cytokine predominantly produced by monocytes/macrophages and T cells, inhibits several functions of dendritic cells (DC), monocytes and T cells including their cytokine production, but it stimulates B cell immunoglobulin (Ig) production and cytotoxic T lymphocyte (CTL) generation. A precise knowledge of the mechanisms that control the IL-10 production is therefore highly important for understanding the immunoregulation. The IL-10 production was studied in cultures of freshly isolated human T cells. A rise in intracellular calcium as well as the common γ-chain containing cytokine receptor triggering or CD28 triggering were found to be important signals for IL-10 induction. CD80, CD58, rIL-12 and rIFN-α all had efficacious and independent costimulatory activities on the IL-10 production, while PGE2 was inhibitory. Dependence on autocrine IL-2 signalling was shown by the effects of anti-IL-2 and anti-IL-2R monoclonal antibodies (MoAb), but the IL-10 production proceeded partly IL-2-independent when CD80 provided costimulation. Sensitivity to inhibition by CsA was not removed by CD80 or CD58 costimulation and/or by addition of rIL-12 or rIFN-α, pointing to the absolute requirement for calcineurin activity. These data reveal important differences in the regulatory pathways between IL-10 (a cytokine-inhibitory interleukin) and IL-2 (a cytokine-inducing interleukin), which can potentially be exploited therapeutically. The fact that CsA blocks the production of IL-10, which itself has important immunosuppressive properties, should be taken into account in defining immunosuppressive treatment schedules which include the use of CsA.

Notes: Interaction of the CD40L (CD154) molecule on activated T cells with its receptor, CD40, on macrophages and dendritic cells (DC) provides a strong signal for interleukin (IL)-12 production. As IL-12 is the most important factor in driving Th precursor (Thp) cells into T(h)elper 1 cells, CD40–CD40L interactions strongly promote Th1 differentiation. Th2 cytokines (IL-4, IL-13, IL-10) on the other hand, are known to inhibit Th1 differentiation, and to promote either directly or indirectly, Th2 differentiation. Inhibition of lipopolysaccharide (LPS)-induced IL-12 production by IL-4, IL-13 and IL-10 is supposed to be one such mechanism. However, we here report that IL-4 and IL-13 enhance p70 IL-12 production and p40 mRNA transcription by human monocytes when the latter are stimulated trough triggering of CD40. This effect on IL-12 induction is most clear in the presence of interferon (IFN)-γ, which upregulates CD40 expression. IL-10 potently inhibits IL-12 production. The increased IL-12 production in the presence of IL-4 and IL-13 is however, not the indirect result of a reduction in IL-10 production, but is most likely owing to a direct effect of IL-4 and IL-13. We conclude that IL-4 and IL-13 enhance rather than decrease the IL-12 production by human monocytes during interaction with T cells. This effect can potentially contribute in vivo to switching of an ongoing Th2 response towards a Th1 response and the findings also support the dominant effect of CD40/CD40L interaction on Th1 development, even in the presence of Th2 cytokines.

Notes: Haptoglobin (Hp) is an acute phase reactant produced by hepatocytes. There is evidence for an immunomodulatory potential of Hp, though there is no clear evidence yet about the mechanisms of this action. We have previously shown that Hp interacts with the β2-integrin CD11b/CD18. In addition, other investigators reported the binding of Hp to B lymphocytes through the CD22 receptor, and to neutrophils through two different receptors.In the present study, we investigated the interaction of haptoglobin with the human mast cell line HMC-1. We report that fluorescein isothiocyanate (FITC)-labelled haptoglobin binds to this cell line and that binding is increased by calcium in a dose- and time-dependent manner. Hp binding sites on HMC-1 were upregulated upon stimulation with phorbol myristate acetate (PMA)/A23187 and after treatment with anti-CD43 and anti-CD44 monoclonal antibodies (MoAbs). HMC-1 cells do not express either CD11b/CD18 or CD22 receptors, indicating that the haptoglobin-binding receptor on this cell line is different from the known receptors. Assessment of cell function showed that Hp inhibits the spontaneous growth of HMC-1 up till 40% at higher Hp concentrations, but it did not exhibit any effect on the expression of CD54 on the release of either tryptase or IL-1ra.In conclusion, haptoglobin binds specifically to human mast cells via a receptor different from CD11b/CD18 and CD22, and may play a role in the modulation of mast cell functions. Exploration of Hp effects in mast cell-dependent diseases such as allergic rhinitis and urticaria seems warranted.

Notes: Background T-helper type 2 (Th2) cells play an important role in the pathogenesis of allergic diseases. Recent studies have demonstrated that allergen-specific T cells can also be found in the blood of healthy individuals. Both IL-10 and IFN-γ might modulate the induction and maintenance of allergen-specific tolerance.Aim To study the phenotype and functional characteristics of allergen-specific T cells in healthy non-atopic children.Methods Peripheral blood mononuclear cells (PBMC) from 13 symptomatic house dust mite (HDM)-allergic children and from nine matched healthy control children were stimulated with recombinant (r)Der p 2, a major allergen from HDMs.Results Stimulation with rDer p 2 resulted in Th2 cytokine production in cultures of PBMC from allergic but not from healthy children. In contrast, IL-10 and IFN-γ were induced in PBMC cultures from both healthy and HDM-allergic children. Intracellular staining revealed that IL-10 and IFN-γ are largely produced by the same T cells. Stimulation of T cells from healthy children with rDer p 2 also induced expression of inducible costimulator (ICOS) on a small T cell subset.Conclusion Allergen-specific memory T cells from healthy non-atopic children produce IL-10 and IFN-γ (but not Th2 cytokines) and express ICOS upon stimulation. These cells might be responsible for a normal immune balance after allergen encounter in non-atopics.

Notes: Background Allergic rhinitis is a risk factor for the development of asthma. About 80% of asthmatic patients also have rhinitis. However, the pattern of induction of allergic rhinitis and asthma remains unclear.Objective The purpose of this study was to investigate the development of upper airway inflammation in mice during the development of an asthma-like disease and after an acute allergen provocation.Methods BALB-c mice were sensitized intraperitoneally (i.p) to ovalbumin (OA, days 1–13) and were challenged with aerosols of either OA or saline on 8 consecutive days (days 33–40). In a second experiment, chronic exposure for 8 days was followed by 10 days of rest and then an acute nebulized allergen provocation was performed (day 50). Inflammatory parameters were investigated at different time-points.Results Upper and lower eosinophilic airway inflammation were simultaneously induced in the course of repeated inhalations of nebulized OA, as shown by analyses of nasal and broncho-alveolar lavage fluids and histological sections of the nose and bronchi. Mice that developed bronchial hyper-responsiveness also had increased thickness of the nasal mucosa on magnetic resonance image (MRI) scans. When chronic exposure was followed by acute allergen provocation, the latter caused a systemic increase in IL-5 levels, with a concomitant rise in blood and airway eosinophils, primarily in the nose.Conclusions Simultaneous induction of eosinophilic inflammation in the nose and lungs was found in a mouse model of respiratory allergy. These findings support the viewpoint that upper and lower airway disease represent a continuum of inflammation involving one common airway and provide evidence for the concept of global airway inflammation after inhalation of allergen.

Notes: Background T helper (Th)2 cells play an important role in the development of IgE-mediated diseases, with local overproduction of Th2 cytokines (IL-4, IL-5 and IL-13) at the site of allergic inflammation. Furthermore, IL-10 has been suggested to play a modulatory role in the induction and maintenance of allergen-specific tolerance in human atopic diseases.Aim We studied whether circulating allergen-specific Th2 cells persist outside the season of exposure in patients mono-sensitized to birch pollen and whether healthy control individuals also have allergen-specific Th2 cells. We also studied whether IL-10-producing allergen-specific T cells can be found in circulation either in healthy controls or in allergic patients.Methods Blood was drawn outside the birch-pollen season from 15 birch-pollen-allergic patients, with seasonal respiratory symptoms and with (n=12) or without (n=3) oral allergy syndrome, and from 10 matched healthy controls. Peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with recombinant Bet v 1 allergen, control antigen tetanus toxoid (TT) and anti-CD3/CD80. In part of the cultures, rIL-4 was added in order to reinforce the allergen-specific Th2 cell responses.Results In the presence of rBet v 1, T cells from allergic patients, but not from healthy controls, produced IL-4, IL-5 and IL-13. IL-5 production by patients' T cells was further enhanced by adding more IL-4. In contrast, rBet v 1 together with IL-4-induced significant IL-10 production in control subjects but not in patients. Both Th1 and Th2 cytokines were equally induced by polyclonal stimulation in allergic patients and controls, but in the presence of IL-4, polyclonally induced IL-10 production was lower in the patient group.Conclusion rBet v 1-specific Th2 cells circulate outside the season of exposure in the blood of birch-pollen-allergic subjects but not in healthy controls. Allergen-specific T cells were also demonstrated in controls but these cells produce IL-10 when stimulated with rBet v 1 in the presence of IL-4. Our data reveal a different allergen-induced cytokine profile in birch-pollen-allergic patients vs. controls, and suggest that a regulatory mechanism involving IL-4-induced allergen-specific IL-10 production might be defective in allergic subjects.

Notes: Background Sex hormones might affect the severity and evolution of bronchial asthma. From existing literature, there exists, however, no convincing evidence for either exacerbation or improvement of allergic symptoms by progesterone.Objective This study was aimed to explore the effect of exogenously administered progesterone in a mouse model of allergic asthma.Methods BALB/c mice were sensitized to ovalbumin (OVA) by intraperitoneal injections with OVA followed by chronic inhalation of nebulized OVA or physiologic saline (Sal). Medroxyprogesterone acetate or placebo was instilled daily into the oesophagus before and during the inhalatory OVA challenge phase.Results Progesterone worsened allergic airway inflammation in OVA-challenged mice, as evidenced by enhanced bronchial responsiveness to inhaled metacholine and increased bronchial eosinophilia. Elevated airway eosinophilia corresponded with higher bronchial and systemic IL-5 levels in the progesterone group. The ratio of IL-4/IFN-γ levels in bronchoalveolar lavage fluid and numbers of eosinophil colony-forming units in the bone marrow were also elevated in the latter group. Progesterone, however, did not influence allergen-specific IgE production, nor did it affect bronchial responses in Sal-challenged mice.Conclusion Our data show that exogenously administered progesterone aggravates the phenotype of eosinophilic airway inflammation in mice by enhancing systemic IL-5 production. Progesterone also increases bronchial hyper-reactivity.

Notes: Recent epidemiological and clinical data indicate that allergic rhinitis and asthma coexist and should be considered as one airway allergy syndrome. In spite of the importance of this new concept of global airway allergy, it has not fundamentally changed our daily diagnostic and therapeutic strategies so far because of the lack of essential clues to understand the correlation between allergic inflammation in upper and lower airways. Because of the resemblance of experimentally induced allergic airway inflammation in mice to inflamed airways of allergic patients, mouse models can enhance our insight into mechanisms underlying the global airway allergy syndrome. We here review data generated in mice that are relevant for understanding the development of airway allergy and provide new options for research on the so-called ‘united airway disease’.