The in vivo depletion of CD4+ T cells prevents antigen-induced eosinophil infiltration into mouse skin.

In order to determine the role of CD4+ T cells and CD8+ T cells in causing antigen-induced eosinophil infiltration into the site of late-phase reaction (LPR), we examined the effect of the in vivo depletion of CD4+ T cells and CD8+ T cells on antigen-induced eosinophil infiltration into mouse skin. Eosinophil infiltration into the skin of ovalbumin (OA)-sensitized BALB/c mice was biphasic after subcutaneous OA challenge, reaching the first peak at 6 h and the second peak at 24 to 48 h. The in vivo depletion of CD4+ T cells by pretreatment with anti-L3T4 monoclonal antibody (mAb) significantly decreased the second peak (at 24 h and 48 h), but not the first peak (at 6 h), of OA-induced eosinophil infiltration into the skin of OA-sensitized mice. However, the depletion of CD8+ T cells by pretreatment with anti-Lyt-2 mAb had no significant effect on either the first or second peak of OA-induced cutaneous eosinophilia in the mouse. These results indicate that CD4+ T cells, but not CD8+ T cells, play an important role in causing antigen-induced eosinophil recruitment of cutaneous LPR.     

Interleukin 25 in allergic airway inflammation

T helper 2 (Th2) cells induce allergic inflammation through the production of cytokines such as interleukin (IL)-4, IL-5 and IL-13. Recently, it has been demonstrated that a novel IL-17 family cytokine IL-25 (IL-17E) is a product of activated Th2 cells and mast cells. Interestingly, when systemically administered to mice, IL-25 induces IL-4, IL-5 and IL-13 production from undefined non-T/non-B cells and then induces Th2-type immune responses such as blood eosinophilia and increased serum immunoglobulin E levels. In addition, we have recently shown that IL-25 mRNA is expressed in the lung after an inhaled antigen challenge in sensitized mice and that neutralization of the produced IL-25 by soluble IL-25 receptor decreases antigen-induced eosinophil and CD4+ T cell recruitment into the airways. Moreover, we have shown that the enforced expression of IL-25 in the lung significantly enhances antigen-induced Th2 cytokine production and eosinophil recruitment into the airways, and that the IL-25-mediated enhancement of antigen-induced eosinophil recruitment is inhibited by the depletion of CD4+ T cells. Thus, it is suggested that IL-25 plays an important role in enhancing allergic airway inflammation by a CD4+ T-cell-dependent mechanism.     

The expression of murine eutaneous late phase reaction requires both IgE antibodies and CD4 T eells

Background Exposure of atopic patients to a specific allergen evokes an immediate response which is followed, in many cases, by a late phase reaction (LPR) some hours later. Here we have examined the immunological mechanisms required for the expression of cutaneous LPR in mice. Methods BALB/c mice were immunized by i.p. injection of ovalbumin (OVA) and alum actively or by i.v. injection of anti-OVA IgE monoclonal antibody (mAb) passively. After challenge by intradermal injection of OVA into ears, the changes in ear thickness, the number of eosinophils, and the levels of IL4 and IFN-γ protein at the site of antigen challenge were examined. Results Actively immunized mice developed a biphasic response at the site of OVA injection, while mice passively immunized with IgE anti-OVA mAb displayed a strong early response but no LPR. Cell transfer experiments using BALB/c nu/nu mice revealed that both OVA-specific IgE mAb and OVA-primed CD4 T cells were required to evoke LPR. Moreover, LPR was associated with increased levels of IL-4 production concomitant with reduced IFN-γ production and was abolished by pretreatment with anti-IL-4 neutralizing mAb. Conclusion It is suggested that murine cutaneous LPR against OVA is a type 2 inflammatory response in which both IgH antibodies and CD4 T cells play an obligatory role.     

High-dose oral tolerance prevents antigen-induced eosinophil recruitment into the mouse airways

We have previously shown that antigen-induced eosinophil recruitment into the tissue of sensitized mice is mediated by CD4+ T cells and IL- 5. To determine whether the induction of oral tolerance down-regulates antigen-induced eosinophil recruitment into the tissue, we studied the effect of oral administration of a protein antigen on antigen-induced eosinophil infiltration in the trachea of sensitized mice, on antigen- induced CD4+ T cell infiltration and IL-5 production in the airways, and on the in vitro production of IL-2, IL-4, IL-5 and IFN-gamma in spleen cells of the mice. Oral administration of a protein antigen in high doses inhibited antigen-induced eosinophil infiltration in the trachea and IgE antibody production in mice in an antigen-specific manner. The oral administration of antigen also suppressed both CD4+ T cell recruitment into the trachea and IL-5 levels in the bronchoalveolar lavage fluids of the mice after antigen inhalation. In vitro antigen-induced production of IL-2, IFN-gamma, IL-4 and IL-5 was decreased in spleen cells of antigen-fed mice, indicating the induction of both Th1 and Th2 cell tolerance in vivo. On the other hand, pretreatment with anti-transforming growth factor-beta antibody at the time of immunization with antigen had no significant effect on the inhibition of antigen-induced eosinophil recruitment and IgE antibody production in antigen-fed mice. Finally, antigen-specific CD4+ T cells were not deleted in TCR transgenic mice after antigen feeding by FACS analysis. Taken together, these results indicate that high-dose oral tolerance induces not only Th1 but also Th2 cell tolerance in vivo and thereby inhibits antigen-induced eosinophil recruitment into the tissue.      

Monoclonal antibody to CD4+ T cells abrogates genetic resistance to Haemonchus contortus in sheep.

The roles of CD4+ and CD8+ T cells in genetically determined resistance of sheep to Haemonchus contortus (a natural host-parasite relationship) was investigated by selectively depleting genetically resistant merino lambs of their CD4+ or CD8+ T cells by treatment with mouse monoclonal antibody (mAb) specific for the appropriate determinant before and during challenge infection. Administration of anti-CD4 mAb to genetically resistant lambs completely abrogated their expression of genetic resistance as indicated by significantly higher faecal egg output and worm burdens found in the CD4+ T-cell-depleted lambs compared with those of controls. Host responses associated with resistance to H. contortus including mucosal mast cell hyperplasia and tissue eosinophilia were also significantly suppressed in CD4-depleted lambs. The development of anamnestic anti-parasite antibody responses were also significantly inhibited by anti-CD4 mAb. Furthermore, anti-CD4 mAb abolished differences in host responses between genetically resistant and random-bred (susceptible) lambs. In contrast, depletion of CD8+ T cells had no effect on genetic resistance; faecal egg output, worm counts, mast cells and eosinophil responses in CD8-depleted lambs were not significantly different from those in controls. Together, these results suggest that CD4+ T cells play a pivotal role in mediating genetic resistance to H. contortus, and in the generation of mucosal mast cell hyperplasia, tissue eosinophilia and anti-Haemonchus antibody. CD8+ T cells appear to play no protective role. The possible mechanisms by which CD4+ T cells might mediate anti-parasite resistance are discussed.     

Lipid A analogue, ONO-4007, inhibits IgE response and antigen-induced eosinophilic recruitment into airways in BALB/c mice

BACKGROUND: Since antigen-specific IgE and eosinophils are major inducing factors of allergic inflammation of the airways, both factors are therapeutic targets of asthma. We investigated the effects of ONO-4007, a nontoxic lipid A analogue, on antigen-specific antibody response and the recruitment of eosinophils into airways in murine systems. METHODS: BALB/c mice were injected ONO-4007 intraperitoneally during sensitization with ovalbumin (OVA) and aluminium hydroxide to determine its effects on the antigen-specific antibody response. ONO-4007 was also injected intravenously during either systemic sensitization and inhalation with OVA, or sensitization or inhalation alone to determine its effects on antigen-induced airway inflammation. In vitro effects of ONO-4007 on the functional differentiation of naive CD4+ T cells were investigated by culturing naive CD4+ T cells derived from DO11.10 mice and OVA-pulsed dendritic cells (CDCs) with ONO-4007. RESULTS: ONO-4007 inhibited antigen-specific IgE and IgG1, but not IgG2a responses. ONO-4007 decreased the recruitment of eosinophils and the levels of IL-5 in bronchoalveolar lavage fluid, not only when it was injected during systemic sensitization and inhalation with OVA, but also during inhalation alone. ONO-4007 inhibited the differentiation of IL-4- and IL-13-producing CD4+ T cells in vitro, which was partly mediated by DCs. CONCLUSIONS: ONO-4007 inhibited antigen-specific IgE and IgG1 responses and antigen-induced eosinophil recruitment into the airways in BALB/c mice. These effects were mediated, at least partly, by the modulation of DCs, although there may also be other mechanisms.     

Role of endothelins on lymphocyte accumulation in allergic pleurisy

Endothelins participate in different aspects of inflammatory reactions, including edema formation and eosinophil accumulation in allergic reaction. In this study, we demonstrated a role for endogenous endothelins in eosinophil and T lymphocyte recruitment and cytokine secretion in a murine model of allergic inflammation. Intrathoracic stimulation with endothelin-1 triggered a neutrophil accumulation at 4 h, concomitant with an increase of CD4+ and CD8+ T lymphocyte populations. Antigen challenge in sensitized animals leads to an increase in eosinophil and mononuclear cell numbers at 24 h. Treatment with ETA receptor antagonist (BQ123) inhibited antigen-induced eosinophil and mononuclear cell migration, whereas the selective ETB receptor antagonist BQ-788 was ineffective. The latter effect of BQ-123 was due to inhibition of CD4+ and CD8+ T lymphocytes. Treatment with BQ-123 also inhibited interleukin-5 levels in the exudate and plasma as well as intracellular staining of interleukin-4, interleukin-5, and interferon-gamma in CD4+ lymphocytes. These findings suggest that endogenous endothelins contribute to allergic inflammation by modulating lymphocyte recruitment and cytokine production.     

Mechanisms of eosinophilia in BALB/c-nu/+ and congenitally athymic BALB/c-nu/nu mice infected with Toxocara canis.

We studied the mechanism of eosinophilia in BALB/c-nu/+ (nu/+) and BALB/c-nu/nu (nu/nu) mice infected with Toxocara canis. Eosinophilia with two peaks on days 11 and 21 of infection was observed in infected nu/+ mice, and with a peak on day 11 in nu/nu mice. Interleukin-5 (IL-5) mRNA was expressed on day 5 of infection in the lung and spleen of nu/+ mice and in the lung of nu/nu mice, but not in the spleen of nu/nu mice. Large numbers of eosinophils and lymphocytes infiltrated the lung of both mice 1 week after infection. The number of larvae in the lung was the largest on day 5. Anti-IL-5 monoclonal antibody (mAb) treatment completely inhibited eosinophilia of both mice, with no change of larval distribution. Administration of anti-CD4 or anti-CD3 mAb markedly reduced the second peak of eosinophilia on day 21 of infection in nu/+ mice, and slightly reduced the first peak of eosinophilia on day 11 in both mice. Anti-CD8 mAb had no effect on the eosinophilia. These results suggest that eosinophilia in both mice is caused by IL-5, and that IL-5 is produced by cells other than CD4+ T cells, in addition to CD4+ T cells.     

CD4+ CD45RA+ T cells modulate allergen-induced interleukin 2 responsiveness in human lymphocytes.

Peripheral blood lymphocytes from nonallergic individuals acquired responsiveness to interleukin 2 (IL2) after stimulation with ovalbumin (OVA) or Dermatophagoides farinae (Df) antigens when they were pretreated with the CD45RA antibody, which has been shown to define the suppressor inducer subset of CD4+ cells and also to block its suppressor activity. The effect provided by the CD45RA antibody was lost if the lymphocytes had initially been activated with the OVA of Df antigens. The magnitude of the responses was comparable to the allergen-induced responses observed in OVA- or Df-sensitized lymphocytes from allergic patients. The pre-existing IL2 responsiveness in the patients was not increased by the CD45RA antibody pretreatment. However, the CD45RA antibody pretreatment gave rise to Df-induced IL2 responsiveness in the lymphocytes of the patients sensitized with OVA but not with Df; conversely, OVA-induced IL2 responsiveness was enhanced in Df- but not in OVA-sensitized lymphocytes. The CD45RA antibody apparently acts on CD4+ T cells, but not on CD8+ T cells, to induce the IL2 response. A further dissection of normal CD4+ T cells indicated that CD4+45RA- T cells preferentially respond to IL2 after stimulation with OVA or Df antigens. Since normal CD4+45RA+ T cells did not show antigen-induced IL2 responsiveness even after pretreatment with the CD45RA antibody, it is unlikely that the CD45RA antibody stimulates CD4+45RA+ T cells to become responsive to IL2 after antigenic challenge. Alternatively, CD4+45RA+ T cells may modulate the activity of CD4+45RA- T cells, which are potentially responsive to IL2 by antigenic stimulation and thus provide tolerance in nonallergic lymphocytes. Collectively, a defective suppressor activity of CD4+45RA+ T cells may exist in patients with hen-egg allergy and/or bronchial asthma, which may cause lymphocytes to be hyperreactive to OVA or Df antigens.     

IFN-gamma secretion by CD8T cells inhibits allergen-induced airway eosinophilia but not late airway responses

BACKGROUND: CD8+T cells can suppress allergen-induced late airway responses (LARs) and airway inflammation. OBJECTIVE: To test the hypothesis that the suppression of LARs and airway eosinophilia by CD8+T cells is IFN-gamma mediated, we tested the effects of adoptively transferred CD8+T cells, in which IFN-gamma synthesis was inhibited by an antisense (AS) oligodeoxynucleotide (ODN), on the airway responses of a rat model of allergic asthma. METHODS: CD8+T cells were harvested from the cervical lymph nodes of ovalbumin (OVA)-sensitized Brown Norway rats for administration to other actively sensitized syngeneic rats. CD8+T cells (2 x 10(6)) were incubated for 6 hours with 2 micromol/L AS ODN or sense ODN and were injected intraperitoneally into recipients; inhibition of IFN-gamma expression in vitro by AS ODN was shown by means of flow cytometry. Two days later, rats were challenged with aerosolized OVA. RESULTS: OVA-induced LAR and bronchoalveolar lavage (BAL) fluid eosinophilia were suppressed by sense ODN-treated CD8+T cells. IFN-gamma expression in BAL cells was elevated in these animals. IFN-gamma expression in BAL cells was at control levels in recipients of AS ODN-treated CD8+ cells, confirming the success of the AS treatment in vivo. BAL eosinophilia was also largely restored in the AS ODN treatment group. In contrast, the CD8+T cell-induced suppression of the LAR was not significantly affected by AS ODN pretreatment. CONCLUSIONS: These results indicate that CD8+T cells inhibit airway eosinophilia through secretion of IFN-gamma but may suppress the LAR by means of other mechanisms.     

Eosinophilia, IgE production, and cytokine production by lung T cells in surface CD4-deficient mutant mice infected with Toxocara canis.

Mutant mice deficient in CD4+ T cells and their normal and heterozygous littermates were infected with Toxocara canis, and compared for eosinophilia, total and Toxocara-specific immunoglobulin E (IgE) production, and in vitro cytokine production by lung cells. The numbers of eosinophils in the peripheral blood of normal and heterozygous mice peaked on days 10 and 21, although mutant mice showed eosinophilia with a peak on day 10. This indicates that the first peak on day 10 is CD4 independent and the second peak is CD4 dependent. Before infection, the levels of total IgE had no significant difference among the three groups of mice. Total and Toxocara-specific IgE in all genotypes of mice increased after infection, and was the highest in normal mice and the lowest in mutant mice. In vitro production of interleukin (IL)-5 and IL-4 by total lung cells was the highest in normal mice and the lowest in mutant mice. CD4+ and CD4- CD8- T lymphocytes, but not CD8+ T lymphocytes produced IL-5 and IL-4 when incubated with anti-CD3 monoclonal antibody (mAb) and lung-adherent cells. These results indicated that IL-5 and IL-4 were produced mainly by CD4+ cells and partly by CD4- CD8- cells, but not by CD8+ cells. In addition, cytokine production by CD4+ cells was affected by the number of CD4 molecules on their surface.     

Astragaloside IV attenuates allergic inflammation by regulation Th1/Th2 cytokine and enhancement CD4CD25Foxp3 T cells in ovalbumin-induced asthma

Astragaloside IV is the chief ingredient of Radix Astragali, which has been used in the Traditional Chinese Medicine as a major component of many polyherbal formulations for the repair and regeneration of injured organ and tissues. We tested the anti-asthmatic effects of AST IV and the possible mechanisms. BALB/c mice that were sensitized and challenged to ovalbumin (OVA) were treated with AST IV (40 mg/kg and 20 mg/kg) 1 h before they were challenged with OVA. Our study demonstrated that AST IV inhibited OVA-induced increases in eosinophil count; interleukin (IL)-4 level were recovered in bronchoalveolar lavage fluid increased IFN-γ and IL-10 levels in bronchoalveolar lavage fluid. Histological studies demonstrated that AST IV substantially inhibited OVA-induced eosinophilia in lung tissue. Flow cytometry studies demonstrated that AST IV substantially increased CD4⁺CD25⁺Foxp3 T cells (Treg). Furthermore quantitative real-time (qPCR) studies demonstrated that AST IV substantially enhanced Foxp3 mRNA expression in lung tissue. These findings suggest that AST IV may effectively ameliorate the progression of airway inflammation and could be used as a therapy for patients with allergic inflammation.     

Interleukin-17 orchestrates the granulocyte influx into airways after allergen inhalation in a mouse model of allergic asthma

Interleukin (IL)-17 is produced by activated memory CD4(+) cells and induces cytokines and chemokines that stimulate neutrophil generation and recruitment. Here, we investigated the involvement of IL-17 in the bronchial influx of neutrophils in experimental allergic asthma. Inhalation of nebulized ovalbumin (OVA) by sensitized mice with bronchial eosinophilic inflammation resulting from chronic OVA exposure induced early IL-17 mRNA expression in inflamed lung tissue, concomitant with a prominent bronchial neutrophilic influx. Anti-IL-17 monoclonal antibodies (mAb) injected before allergen inhalation strongly reduced bronchial neutrophilic influx, in a manner equally as potent as the anti-inflammatory dexamethasone. Remarkably, anti-IL-17 mAb significantly enhanced IL-5 levels in both BAL fluid and serum, and aggravated allergen-induced bronchial eosinophilia. In another series of experiments, anti-IL-17 mAb were given repeatedly during the inhalatory challenge phase with OVA of sensitized mice. This treatment regimen abated bronchial neutrophilia in parallel with reduction of bone marrow and blood neutrophilia. In addition, anti-IL-17 mAb treatment elevated eosinophil counts in the bone marrow and bronchial IL-5 production, without alteration of allergen-induced bronchial hyperresponsiveness. In summary, our results demonstrate that IL-17 expression in airways is upregulated upon allergen inhalation, and constitutes the link between allergen-induced T cell activation and neutrophilic influx. Because neutrophils may be important in airway remodeling in chronic severe asthma, targeting IL-17 may hold therapeutic potential in human asthma.     

CD4+CD25+ T cell depletion impairs tolerance induction in a murine model of asthma

Background Regulatory T cells (Tregs) are key players in controlling the development of airway inflammation. However, their role in the mechanisms leading to tolerance in established allergic asthma is unclear. Objective To examine the role of Tregs in tolerance induction in a murine model of asthma. Methods Ovalbumin (OVA) sensitized asthmatic mice were depleted or not of CD25⁺ T cells by anti‐CD25 PC61 monoclonal antibody (mAb) before intranasal treatment (INT) with OVA, then challenged with OVA aerosol. To further evaluate the respective regulatory activity of CD4⁺CD25⁺ and CD4⁺CD25^? T cells, both T cell subsets were transferred from tolerized or non‐tolerized animals to asthmatic recipients. Bronchoalveolar lavage fluid (BALF), T cell proliferation and cytokine secretion were examined. Results Intranasal treatment with OVA led to increased levels of IL‐10, TGF‐β and IL‐17 in lung homogenates, inhibition of eosinophil recruitment into the BALF and antigen specific T cell hyporesponsiveness. CD4⁺CD25⁺Foxp3⁺ T cells were markedly upregulated in lungs and suppressed in vitro and in vivo OVA‐specific T cell responses. Depletion of CD25⁺ cells before OVA INT severely hampered tolerance induction as indicated by a strong recruitment of eosinophils into BALF and a vigorous T cell response to OVA upon challenge. However, the transfer of CD4⁺CD25^? T cells not only suppressed antigen specific T cell responsiveness but also significantly reduced eosinophil recruitment as opposed to CD4⁺CD25⁺ T cells. As compared with control mice, a significantly higher proportion of CD4⁺CD25^? T cells from OVA treated mice expressed mTGF‐β. Conclusion Both CD4⁺CD25⁺ and CD4⁺CD25^? T cells appear to be essential to tolerance induction. The relationship between both subsets and the mechanisms of their regulatory activity will have to be further analyzed.     

IgE-dependent enhancement of Th2 cell-mediated allergic inflammation in the airways

T helper 2 (Th2) cell-derived cytokines, including interleukin (IL)-4, IL-5 and IL-13, play important roles in causing allergic airway inflammation. In contrast to Th2 cells, however, the role of IgE and mast cells in inducing allergic airway inflammation is not understood fully. In the present study, we addressed this point using transgenic mice expressing trinitrophenyl (TNP)-specific IgE (TNP-IgE mice), which enable us to investigate the role of IgE without the influence of antigen-specific T cell activation and other immunoglobulins. When the corresponding antigen, TNP-BSA, was administered intranasally to TNP-IgE mice, a large number of CD4+ T cells were recruited into the airways. In contrast, TNP-BSA administration did not induce eosinophil recruitment into the airways or airway hyperreactivity. Furthermore, when ovalbumin (OVA)-specific Th2 cells were transferred to TNP-IgE mice and the mice were challenged with inhaled OVA, TNP-BSA administration increased OVA-specific T cell recruitment and then enhanced Th2 cell-mediated eosinophil recruitment into the airways. These results indicate that IgE-induced mast cell activation principally induces CD4+ T cell recruitment into the airways and thus plays an important role in enhancing Th2 cell-mediated eosinophilic airway inflammation by recruiting Th2 cells into the site of allergic inflammation.     

Resident CD8+ T cells suppress CD4+ T cell-dependent late allergic airway responses

BACKGROUND: The role of CD8+ T cells in the immune response to airway challenge with an allergen is poorly understood. OBJECTIVE: The aim of this study was to test the hypothesis that resident naive CD8+ T cells modulate the magnitude of CD4+ T cell-dependent allergic airway responses. METHODS: Cervical lymph node CD4+ T cells (2 x 10(6)) were harvested from ovalbumin (OVA)- or sham-sensitized rats and injected intraperitoneally into naive Brown Norway recipients. The recipients were treated with a CD8alpha mAb (OX-8) to deplete the resident CD8+ T cells (n = 12) or mouse ascites (n = 12). Two days after adoptive transfer, the recipient animals were OVA challenged, lung resistance was measured for 8 hours, and bronchoalveolar lavage (BAL) was performed. RESULTS: After OVA challenge, primed CD4-transferred CD8-depleted rats had larger early airway responses and late airway responses compared with primed CD4-transferred CD8-nondepleted rats (early airway responses: 158.6% +/- 19.2% vs 115.7% +/- 5.9%, P < .05; late airway responses: 8.5% +/- 1.7% vs 4.4% +/- 0.9%, P < .05). BAL eosinophilia was also greater (4.67% +/- 0.45% vs 2.34 +/- 0.26%, P < .01). The cells in BAL fluid expressing IL-4 mRNA were not significantly changed by CD8 depletion, but IL-5 mRNA+ cells were higher in number, and IFN-gamma mRNA+ cells were fewer in the CD8-depleted group. CONCLUSIONS: Resident CD8+ T cells downregulate the late allergic response and airway inflammation evoked by CD4+ T-cell transfers in Brown Norway rats. This downregulation does not require antigen priming.     

Correlation between eosinophilia induced by CD4(+) T cells and bronchial hyper-responsiveness

The relationship between CD4(+) T cell-mediated airway eosinophilic inflammation and bronchial hyper-responsiveness (BHR) was investigated. Ovalbumin-reactive T(h)0 clones were adoptively transferred to unprimed BALB/c mice and then the mice were challenged by inhalation of the relevant antigen. Upon antigen provocation, infused T(h) clones infiltrated into the airways, followed by the accumulation and degranulation of eosinophils, goblet cell hyperplasia, edema and increase in bronchial responsiveness to acetylcholine. Transfer of several clones that differed in the levels of IL-5 production revealed that the magnitude of in vivo eosinophilia strongly correlated with the IL-5-producing capacity of the infused T(h) clones. Administration of anti-IL-5 mAb almost completely suppressed antigen-induced eosinophilic inflammation and BHR. Administration of anti-IL-4 mAb or anti-IFN-gamma mAb enhanced the eosinophilia and BHR, whereas anti-IL-2 mAb did not affect them. The number of accumulated eosinophils significantly correlated with the intensity of BHR. Our present results clearly demonstrated that CD4(+) T cells induced BHR as a result of eosinophilic inflammation. IL-5 totally regulated both responses.     

In vivo inhibition by a monoclonal antibody to CD4+ T cells of humoral and cellular immunity in sheep.

The ability of intravenously injected anti-CD4 and anti-CD8 monoclonal antibody (mAb) to deplete specific lymphocyte subsets in vivo and their effects on antibody responses to ovalbumin (OVA) and Brucella abortus, and skin reactivity to T-cell mitogens was examined in merino lambs. Repeated administration of anti-CD4 or anti-CD8 mAb caused a specific and sustained depletion of target cells from peripheral blood. Anti-CD4 mAb significantly inhibited the in vivo antibody response to OVA but had no effect on the antibody response to LPS of B. abortus. In contrast, antibody responses to both OVA and B. abortus lipopolysaccharides (LPS) remained unaffected in lambs depleted of their CD8+ T lymphocytes. These results confirm the T-cell dependence and independence of antibody responses to OVA and LPS, respectively. Skin reactions elicited by intradermal injections of phytohaemagglutinin (PHA) and concanavalin A (Con A) were also significantly suppressed in lambs depleted of their CD4+ T cells, but treatment with anti-CD8 mAb had no effect on skin responsiveness. Together, these results suggest that mAb can be extremely effective at selectively depleting lymphocyte subsets in vivo and can be used for studying various aspects of immunoregulation and immunity in sheep.     

Induction of Th2 cell tolerance to a soluble antigen by blockade of the LFA-1-dependent pathway prevents allergic inflammation

In this article, we show that induction of Th2 cell tolerance prevents antigen-induced eosinophil recruitment into the tissue and IgE antibody production, and that ICAM-1/LFA-1 interaction is involved as a costimulatory signal in inducing T cell tolerance to a soluble antigen. In vivo pretreatment with anti-ICAM-1 monoclonal antibody (mAb), anti-LFA-1 mAb, and a soluble antigen inhibited antigen-induced eosinophil recruitment into the airways and IgE antibody production in mice in an antigen-specific manner. In vitro antigen-induced IL-2, IL-4 and IL-5 production were decreased in spleen cells of the mice pretreated with the two mAbs and the antigen, indicating the induction of both Th1 and Th2 cell tolerance in vivo. These results suggest that the induction of antigen-specific Th2 cell tolerance by allergen immunotherapy with blockade of the ICAM-/LFA-1 interaction would be a rational therapeutic approach to allergic inflammation such as asthma.     

Antigen presentation by local macrophages promotes nonallergic airway responses in sensitized mice

Local inflammatory responses involve relocating immune functions generated by previous immunization to confined parts of the body, and hence are presumed to reflect the prevailing systemic immune bias. To verify to what extent local antigen-presenting cells (APCs) may modulate immune inflammation, we analyzed the consequences of antigen presentation by macrophages on Th2-dependent airway inflammation in ovalbumin (OVA)-sensitized mice. In contrast to challenge with free OVA, which triggers airway eosinophilia and Th2 cell recruitment, intratracheal instillation of immortalized spleen macrophages (Mf4/4 cells), pulsed with OVA, promoted a nonallergic airway response featuring recruitment of interferon-gamma-producing Th1 cells. Combining OVA-Mf4/4 instillation with OVA inhalation strongly reduced airway eosinophilia. Inflammation repression persisted after secondary OVA challenge and depended on the antigen-presenting ability of the macrophages. Arguing against Th1-mediated counter-regulation, Th1/Th2 ratios remained unaltered in macrophage-treated/OVA-challenged mice. In contrast, levels of interleukin-4 and interleukin-13 mRNA in lung tissue CD4+ T cells were strongly downregulated, indicating a suppression of Th2 cell activation. These results document a role for local macrophages/APCs in controlling the nature and intensity of local immune inflammatory responses. The resulting segregation of systemic and local levels of immune reactivity may enable local inflammation tolerance; it is a nonallergic airway response despite systemic sensitization.