A comparison of cell-mediated immunity and suppressor T-cell function in asthmatic and normal children

Low-dose theophylline in childhood asthma: a placebo-controlled, double-blind study

Regular anti-inflammatory treatment is essential in treating persistent asthma. Most commonly, inhaled corticosteroids (ICS) are used. However, especially in children, there is concern about the long-term safety of ICS such that doses should be kept to a minimum. The use of theophylline has decreased because of frequent side-effects in therapeutic doses. In adults, there have been reports about an immunomodulatory effect of low-dose theophylline. To study the clinical and immunomodulatory effect in children, 36 patients (mean age 12.5 SD 2.4 years) with moderate, persistent asthma on regular ICS were recruited into a placebo-controlled, double-blind study. After a 6-week run-in period, patients received either theophylline 10 mg/kg bodyweight or placebo for 12 weeks. Diary cards, lung function, peripheral blood lymphocyte subpopulations and serum eosinophil cationic protein (sECP) were assessed. In the treatment group, mean serum theophylline was 7.1 mg/l. There was no change in symptoms or use of rescue medication. Mean (SD) peak expiratory flow (PEF) increased from 86% (24) to 95% (18) predicted. sECP decreased from 43.2 microg/l (32.5) to 26.5 microg/l (16.9) (p = 0.02). Lymphocyte subpopulations did not change. The study failed to show a beneficial clinical or an immunomodulatory effect of theophylline when used in low doses. These results do not support a more important role of theophylline in the long-term treatment of moderate childhood asthma.

Cytokines as targets for the inhibition of eosinophilic inflammation

Eosinophilic inflammation is thought to play a central role in the pathogenesis of asthma. The immunoregulatory effects of interleukin (IL)-4, IL-5 and immunoglobulin (Ig)E suggest that these molecules play key roles in the effector function of eosinophils and mast cells. IL-4 regulates the development of CD4+ TH2-type cells, which elicit essential signals through IL-4 and IL-5 for the regulation of IgE production and eosinophilia, respectively. IL-5-regulated pulmonary eosinophilia and airways dysfunction can also occur independently of IL-4 and allergen-specific Igs. Such IL-4-independent pathways may also play a substantive role in the aetiology of asthma. Thus, evidence is now emerging that allergic airways disease is regulated by humoral and cell-mediated components. The essential and specific role of IL-5 in regulating eosinophilia, and the subsequent involvement of this leukocyte in the induction of lung damage and airways dysfunction, identifies IL-5 as a primary therapeutic target for the relief of airways dysfunction in asthma.

Requirement for CD8+ T cells in the development of airway hyperresponsiveness in a marine model of airway sensitization

To study the role of CD8+ T cells in allergic sensitization, we examined the effects of in vivo depletion of CD8+ T cells prior to sensitization on IgE production, immediate type cutaneous hypersensitivity and development of altered airway responsiveness. BALB/c mice were thymectomized and treated with anti-CD8 antibody resulting in depletion of CD8+ T cells (<1%) in spleen and lymphoid tissues. In these mice, sensitization to ovalbumin (OVA) via the airways still resulted in IgE anti-OVA responses and immediate cutaneous reactions to OVA, but the animals were unable to develop airway hyperresponsiveness, eosinophil infiltration of the lung parenchyma, or IL-5 production in the local lymph nodes of the airway. Transfer of CD8+ T cells from naive animals during sensitization (on day 8 of the 10-d protocol) fully restored the ability to develop airway hyperresponsiveness and this was accompanied by IL-5 production and eosinophil accumulation in the lung. These data indicate a critical role for CD8+ T cells in the production of IL-5 and the development of altered airway responsiveness after antigen sensitization through the airways.

Depletion of OX-8 lymphocytes from the blood and airways using monoclonal antibodies enhances the late airway response in rats

Recent evidence supports a role for T lymphocytes in allergic airway responses. We hypothesized that reducing blood T suppressor cells (Ts) might increase the late airway response (LR). Sprague-Dawley (SD) rats were sensitized with ovalbumin (OA). On days 8, 10, and 12, post-sensitization test SD (n = 14) received monoclonal antibody intravenously (OX-8; 1 mg) specific to rat Ts. Controls received saline (n = 7) or mouse ascites IgG (n = 7). On day 14, animals were challenged with OA aerosol (5% wt/vol) for 5 min, lung resistance was recorded for 8 h (n = 18) and bronchoalveolar lavage was performed. The LR was determined from the area under the lung resistance vs time curve from 75 to 480 min after challenge. In the remaining 10 rats, airway lymphocyte subsets were measured 8 h after OA aerosol challenge in minced and digested lungs. A decrease in percentage of blood and airway Ts, respectively, in test animals was observed vs controls (blood: 6.27 +/- 0.84 vs 32.95 +/- 1.94, P < 0.001); (airway: 5.05 +/- 0.66 vs 24.5 +/- 3.05, P < 0.02). Blood and airway helper T lymphocytes did not differ between test and control animals. The LR was significantly increased in test (22.89 +/- 3.92) vs controls (4.22 +/- 2.18, P < 0.001). Bronchoalveolar lavage macrophages, neutrophils and lymphocytes, and serum OA-specific IgE were also significantly elevated (P < 0.05) in test animals. We conclude that Ts play an important role in attenuating the LR in SD rats.

Inflammation and airway reactivity in asthma

The increased airway reactivity characteristic of asthma may be due to contraction of airway smooth muscle, mucus hypersecretion, edema and thickening of airway walls, and the presence of serum proteins and inflammatory cells and their products in the airways. Increased airway reactivity in asthma correlates with airway epithelial damage and is clearly related to airway inflammation, a process that most likely involves a complex interaction among mast cells, lymphocytes, eosinophils, and macrophages. Thus, although symptomatic treatment of airway narrowing is best accomplished with bronchial smooth muscle relaxants, treatment of the basic pathophysiologic defect should attempt to reduce airway inflammation. Bronchodilators (inhaled beta-agonists and, occasionally, theophylline), which do not decrease airway reactivity, are often used to treat the symptoms of patients with mild or episodic asthma; inhaled corticosteroids, which do decrease airway inflammation and reactivity, are used to treat patients with more severe symptoms. Methotrexate and cromolyn sodium may also be used, although their role in treating the underlying pathophysiology remains controversial. Identification of new agents that are as effective as corticosteroids but that do not produce their side effects would represent a major therapeutic advance for patients with asthma.

Imbalance of CD4+CD45R+ and CD4+CD29+ T helper cell subsets in patients with atopic diseases

To evaluate the proportion of helper cell subsets we studied 18 children with atopic dermatitis, 30 patients with asthma, 27 healthy age-matched controls aged 1 to 17 years and 11 atopic controls without symptoms related to atopy, aged 9-22 years. Lymphocytes were isolated from heparinized peripheral blood and the proportion of CD4+CD29+ and CD4+CD45R+ cells was determined by double-labelling immunofluorescence. Children with atopic dermatitis yielded a significantly (P less than 0.01) higher proportion of CD4+CD45R+ (median 75%) cells compared with normal controls (median 66.6%), whereas the proportion of CD4+CD29+ cells was significantly (P less than 0.01) lower in patients with atopic dermatitis (median 20.4 versus 29.6%). Interestingly, the percentage of CD4+CD45R+ cells shows an age-dependent decline (r = -0.67, P less than 0.01) in the control group, which is not found in the patient group.

Seasonal variation in suppressor T cell subsets and non-specific suppressor cell function in hay fever sufferers

The helper/suppressor T cell ratio, as defined by monoclonal antibodies, was significantly higher in hay fever sufferers compared with controls (P less than 0.05), but only during or shortly after the pollen season. This was due to a reduction in the suppressor subset, which returned to control values in the winter. There was no significant difference in the non-specific concanavalin A-induced suppressor cell function compared with controls. The mean summer value was significantly lower than the winter value (P less than 0.05), but we cannot be sure that this was not the result of changes in laboratory conditions. No relationship was found between T cell subsets or suppressor cell function and total or specific IgE levels, or between T cell subsets and suppressor cell function. Our findings suggest that in hay fever, reduction in suppressor cell numbers and function is a secondary phenomenon.

T cell responses in allergic rhinitis, asthma and atopic dermatitis

Although clinical responses to allergens have been shown to primarily involve IgE antibodies, there is often no clear correlation between the amount of allergen-specific IgE present in the serum and the nature and severity of allergic symptoms. This observation raises the question of the possible role of non-IgE mediated types of immune responses in this reaction. It is not known to what extent components of T cell-mediated immunity are involved in IgE-mediated reactions but several observations suggest an association between atopic disease and alterations in cellular immune function. These include the frequent association of high serum IgE levels with: (i) several of the primary and acquired immunodeficiencies characterized by partial T cell deficiency; (ii) the defective cell-mediated immunity and resultant recurrent infections seen in the hyper-IgE syndrome; and (iii) the sudden rise in serum IgE levels associated with reduced numbers of suppressor T cells in bone marrow transplant recipients during the acute graft vs host disease. In this review, we will examine the recent evidence suggesting that the T lymphocyte may play a primary role in the pathogenesis of atopic disorders.

Inflammatory cells in bronchial asthma

A diagrammatic representation of the interactions between mediators of hypersensitivity and leukocytes in early, late-phase, and ongoing asthma is shown in Figure 1. Early phase or immediate reactions are largely the result of bronchoconstriction consequent to the release of mediators such as histamine, PGD2, LTC4/D4, and PAF. The principal mediator cell (MC) is the mast cell (although other IgE receptor-bearing cells such as the macrophage, eosinophil, and platelet might also be involved in this immediate response). The stimulus for mediator cell activation may be either immunologic (IgE-dependent) or nonimmunologic (i.e., changes in osmolarity as a result of the respiratory water loss associated with exercise-induced asthma). Late-phase reactions appear to be a consequence of infiltration with neutrophils (N), eosinophils (E), and macrophages (M phi). These cells are recruited and activated either by mast cell-associated chemotactic factors [such as LTB4, PAF, the eosinophil chemotactic factor of anaphylaxis (ECF-A), or high-molecular weight neutrophil chemotactic activity (NCA (HMW))] and/or "lymphokines" derived from T-helper cells (TH) which have been stimulated by antigen processed by the antigen-processing cells (APC). These mononuclear cell interactions are under the control of regulatory T cells [T suppressor (TS) cells] and it is speculated that the availability of these subsets may determine the magnitude of the late-phase response. Lymphokines and monokines which selectively activate neutrophils, eosinophils, and monocytes include LIF, EAF, and IFN-gamma, respectively. Macrophage-derived tumor necrosis factor (TNF) also amplifies the inflammatory response by its capacity to enhance eosinophil cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Leucocytes in asthma

A diagrammatic representation of the interactions between mediators of hypersensitivity and leucocytes in early-, late-phase, and ongoing asthma is shown in Fig. 1. Early-phase or immediate reactions are largely the result of bronchoconstriction consequent to the release of mediators such as histamine, PGD2, LTC4/D4 and PAF. The principal mediator cell (MC) is the mast cell (although other IgE receptor-bearing cells such as the macrophage, eosinophil and platelet might also be involved in this immediate response). The stimulus for mediator cell activation may be either immunologic (IgE-dependent) or non-immunologic (i.e. changes in osmolarity as a result of the respiratory water loss associated with exercise-induced asthma). Late-phase reactions appear to be a consequence of infiltration with neutrophils (N), eosinophils (E) and macrophages (MO). These cells are recruited and activated either by mast cell-associated chemotactic factors [such as LTB4, PAF, the eosinophil chemotactic factor of anaphylaxis (ECF-A) or high molecular weight neutrophil chemotactic activity (NCA (HMW]] and/or "lymphokines" derived from T helper cells (TH) which have been stimulated by antigen processed by the antigen processing cells (APC). These mononuclear cell interactions are under the control of regulatory T cells [T suppressor (TS) cells] and it is speculated that the availability of these subsets may determine the magnitude of the late-phase response. Lymphokines and monokines which selectively activate neutrophils, eosinophils and monocytes include LIF, EAF and INF-gamma respectively. Macrophage-derived tumour necrosis factor (TNF) also amplifies the inflammatory response by its capacity to enhance eosinophil cytotoxicity. Eosinophil-derived agents such as PAF, LTC4, MBP and ECP might be responsible for submucosal oedema and non-specific bronchial hyperreactivity which are characteristic features of late-phase reactions. T cell-derived lymphokines such as EDF (IL-5), together with GM-CSF, might lead to eosinophilopoiesis and account for the prolonged eosinophilia of ongoing chronic asthma. The T cell is prominent in the pathology of chronic asthma and is possibly "chronically activated". Thus lymphocytes, driven by as yet undetermined "antigens" (possibly viral), may perpetuate the inflammatory response in and around the bronchi. IL-5-like products from these putative activated lymphocytes might perpetuate (a) eosinophil production by the bone marrow, (b) its release into the circulation, (c) its migration into bronchial tissue and (d) activation to release PAF, LTC4, MBP, etc.(ABSTRACT TRUNCATED AT 400 WORDS)

Theophylline-induced alterations in cellular immunity in asthmatic patients

Twenty patients with bronchial asthma, on long-term oral therapy with theophylline, demonstrated an increased number of suppressor T-cells and impaired graft vs host reaction. Ten asthmatics on other therapy, not including theophylline, as well as ten normal healthy controls, failed to show similar findings. Elimination of suppressor T-cells corrected the above immunological abnormalities in the theophylline-treated patients, while addition of serum from theophylline-treated asthmatic patients to lymphocytes from normal healthy controls, affected the graft vs host reaction of these lymphocytes. We conclude that theophylline induces quantitative as well as qualitative immunological alterations by increasing the number and activity of suppressor T-cells, which most probably secrete a serum factor, responsible for some of the abnormalities observed.

Effect of oral colchicine on T cell subsets, monocytes and concanavalin A-induced suppressor cell function in asthmatic patients

Asthmatic patients have a deficiency of concanavalin A-(Con A) induced suppressor cell function. We tested whether oral colchicine 0.5 mg twice daily for 7 days could correct this immunoregulatory abnormality. Peripheral blood mononuclear cells were incubated with Con A and then suppression of proliferation was measured by coculture of these cells with healthy volunteers' mononuclear cells and phytohaemagglutinin. Sixteen asthmatic patients had significantly (P less than 0.002) decreased Con A-induced suppressor cell function (17.0 +/- 17.2%, mean +/- s.d.) as compared to 13 healthy volunteers (37.9 +/- 14.9%). Oral colchicine significantly (P less than 0.05) increased, though only partially corrected, these 16 asthmatic patients' Con A-induced suppressor cell function (28.1 +/- 14.3%). Asthmatic patients had an increased number of monocytes (691 +/- 289 vs 388 +/- 271/mm3 for normals, P less than 0.01) and a normal number of lymphocytes, Leu 4+ total T cells, Leu 3+ helper/inducer T cells, and Leu 2+ suppressor/cytotoxic T cells as well as a normal Leu 3/Leu 2 ratio. Oral colchicine significantly (P less than 0.005) decreased the number of monocytes (451 +/- 255/mm3) without significantly affecting the number of lymphocytes, Leu 4+, Leu 3+, or Leu 2+ T cells, or the Leu 3/Leu 2 ratio. These results are consistent with the hypothesis that the deficiency of Con A-induced suppressor cell function in asthmatic patients may be due, in part, to an increased number and/or abnormal activity of monocytes. If so, then oral colchicine may have partially corrected the deficiency of Con A-induced suppressor cell function by decreasing the number and/or modulating the activity of monocytes.

Primary cell-mediated immune response in bronchial asthma. Relationship between primary in vitro and in vivo cell-mediated and antibody responses in patients with asthma and healthy controls

Eleven patients with asthma and ten sex and age matched healthy controls were immunized with the primary immunogen Helix pomatia Haemocyanin (HPH). The amplitude and the kinetics of in vitro cell-mediated immune response were measured by HPH-induced lymphocyte proliferation. Lymphocytes were also challenged in vitro with mitogens and recall antigens. In vivo cell-mediated immunity was determined by inducing delayed type hypersensitivity reactions with HPH. Anti-HPH antibody responses in the IgE, IgG and IgM classes were measured to gain an insight into the relation between cell-mediated and humoral immune responses in patients with asthma and healthy controls. The in vitro and in vivo cell-mediated response and the IgM antibody response did not differ between patients with asthma and controls. The IgE and IgG antibody responses, however, were increased in the patients. IgM antibody response correlated with both the in vitro and in vivo cell-mediated response (R = 0.45, P less than 0.05). IgE and IgG antibody responses however were not correlated with cell-mediated responses. These data suggest that the primary abnormality in immune regulation in patients with asthma concerns the control of the IgE and IgG class antibody responses.

Proliferative response in solid culture of T cells from patients with extrinsic bronchial asthma

T cells proliferative response in both liquid and solid culture conditions (the later prevents direct cell to cell contact) was investigated in nineteen Extrinsic Bronchial Asthma patients (EBA). Tetradecanoyl-phorbol-13-acetate (TPA), a T cell mitogen was used as mitogenic stimulus in both liquid and solid conditions. While the response to phytohemaglutinin (used in liquid culture as reference) was intact, the EBA group showed a significant reduction in the proliferative response to TPA in both culture conditions. Furthermore, when adherent cells were removed prior to TPA stimulation, while the control group showed a significant decrease in proliferation, the already depressed low proliferation of the EBA group remained unchanged. These results suggest the prevalence of suppressor signals in EBA and may indicate heterogeneity of the suppressor cells pool since high levels of total serum IgE were also present in the same patients.

Lymphocyte sub-populations in patients with allergic and non-allergic asthma

The subpopulations of peripheral blood lymphocytes were identified using monoclonal antibodies specific for T lymphocytes (T11 antibodies), B lymphocytes (B1 antibodies), helper/inducer T cells (T4 antibodies) and suppressor/cytotoxic cells (T8 antibodies). Ninety-six subjects, including twenty-five patients with allergic asthma, nineteen patients with non-allergic asthma and fifty-two controls without asthma, were studied. There was no significant difference in the lymphocyte subsets between the allergic and non-allergic asthmatics. When comparing patients with asthma as a group with the controls, a decrease in the number of T8-positive suppressor cells and therefore, an increase in the helper/suppressor cell ratio were demonstrated in the asthmatics. A relative deficiency of suppressor T cells may represent another immunological marker of bronchial asthma.

Deficient concanavalin-A-induced suppressor-cell activity in patients with bronchial asthma, allergic rhinitis and atopic dermatitis

Concanavalin-A (Con-A)-induced suppressor activity against the proliferative response of autologous lymphocytes to phytohaemagglutinin (PHA) was examined in the peripheral-blood lymphocytes from fourteen patients with bronchial asthma, ten patients with allergic rhinitis and eleven patients with atopic dermatitis and compared with eleven simultaneously studied healthy normals. Eight of fourteen patients (57%) with bronchial asthma, eight of ten patients (80%) with allergic rhinitis and five of eleven patients (45%) with atopic dermatitis demonstrated deficient Con-A-induced suppressor function. Abnormal suppressor-cell functions could play an important role in the pathogenesis of atopic states.

Induction of suppressor T cells in asthmatic children by theophylline treatment

The absolute T-cell numbers and function, and the T-suppressor-cell subset were tested in eleven children with extrinsic asthma prior to and 1 month after theophylline treatment. Low mean T-suppressor-cell number and function was found in the asthmatic children, which returned to normal levels and function after 1 month of theophylline treatment. A normal mean T-cell number was found in this group of children prior to, and 1 month after, theophylline treatment. An obvious correlation between the clinical severity of the asthma and the number of T suppressor cells was found. It is suggested that theophylline most probably activated the T suppressor cells in the asthmatic children.

Autologous mixed lymphocyte reaction in man. VII. Autologous mixed lymphocyte reaction in patients with bronchial asthma, allergic rhinitis and atopic dermatitis

The proliferative response of T lymphocyte cultured with autologous non-T lymphocyte is known as the autologous mixed lymphocyte reaction (AMLR). In AMLR, both helper and suppressor functions are generated. In this investigation we have examined T cell proliferative responses in AMLR in 12 patients with bronchial asthma, 10 patients with allergic rhinitis, and 10 patients with atopic dermatitis and compared that with simultaneously studied healthy controls. Our data show that the T cell proliferation in AMLR in patients with bronchial asthma is significantly higher than that of healthy normals. However, AMLR response in patients with allergic rhinitis or atopic dermatitis is comparable to controls. Mechanisms for increased AMLR in patients with bronchial asthma are discussed.