Peripheral blood mononuclear cells (PBMC) and serum were obtained, on two occasions, from 15 asthmatic patients who required oral glucocorticoid therapy for moderate to severe disease exacerbations. Samples were obtained immediately before commencement of oral glucocorticoids (Day 1) and again after 7 days of treatment (Day 7), when lung function had significantly improved. Samples were also isolated on two occasions 7 days apart from a group of seven untreated volunteers. Expression of CD25, human lymphocyte antigen (HLA-)DR, CD45RA, and CD45RO on CD4 and CD8 T lymphocytes was measured by flow cytometry, and serum concentrations of interleukin-5 (IL-5) were measured using an enzyme-linked immunosorbent assay technique. On Day 1 the asthmatic patients showed significantly higher percentages, as compared with the control subjects of CD4 T lymphocytes expressing the markers CD25, HLA-DR, and CD45RO and significantly lower percentages of CD4 T cells expressing CD45RA. After glucocorticoid therapy, the percentages of CD4 T cells expressing CD25, HLA-DR, and CD45RO were significantly reduced in the asthmatic patients, and the percentages of those expressing CD45RA significantly increased so that by Day 7 expression of all four markers was no longer significantly different from that of the control subjects. By contrast, the percentages of CD8 T cells expressing HLA-DR, CD45RA, and CD45RO in the PBMC of the asthmatic patients on Day 1 were not significantly different from those in control subjects, whereas the percentages of CD25 expressing CD8 T cells were only marginally elevated. Glucocorticoid therapy resulted in no significant change in the expression of all four markers on CD T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

T-lymphocyte (T-LC)-derived cytokines have been implicated in asthma pathogenesis. Activation of peripheral blood CD4 but not CD8 T-LC and a Th2-type pattern of elevated cytokine mRNA expression in BAL fluid T-LC have been observed in asthmatics, but the principal source (CD4 or CD8 T-LC) of these cytokines is unknown. Our objective was to measure expression of Th1- and Th2-type cytokine mRNA and spontaneous secretion of IL-3, IL-5, and GM-CSF by peripheral blood CD4 and CD8 T-LC from asthmatics before and after oral glucocorticoid therapy and non-asthmatic controls. We used in situ hybridization to detect mRNA expression in isolated CD4 and CD8 T-LC, and an in vitro eosinophil survival assay to detect secretion of IL-3, IL-5, and GM-CSF in T-LC culture supernatants. Comparing the asthmatics with the controls, elevated percentages of CD4 T-LC expressed mRNA encoding IL-5, IL-4, and GM-CSF (P < 0.02) but not IL-3, IL-2, or IFN-gamma. In CD8 T-LC, mRNA expression was generally low with no significant differences between the groups. In the asthmatics, the percentages of CD4 T-LC expressing IL-5 mRNA correlated with disease severity and the numbers of peripheral blood eosinophils (P < 0.01). Culture supernatants of asthmatic CD4 but not CD8 T-LC exhibited significantly higher (P = 0.0003) eosinophil survival-prolonging activity compared with controls, in which low activity was detected. Inhibition with anti-cytokine antibodies suggested that GM-CSF, and to a lesser extent IL-5 and IL-3, could account for this activity. After oral glucocorticoid therapy of the asthmatics, lung function improved and the percentages of CD4 T-LC expressing mRNA encoding IL-3, IL-5, and GM-CSF but not IL-2, IL-4, or IFN-gamma were reduced (P < 0.04). Secretion of eosinophil survival-prolonging activity by the CD4 T-LC was also reduced (P = 0.004). We conclude that peripheral blood CD4 but not CD8 T-LC from asthmatics express cytokine mRNA in a Th2-type pattern and show elevated secretion of cytokines prolonging eosinophil survival. Glucocorticoid therapy of asthmatics is associated with a reduction in the percentages of CD4 T-LC expressing IL-3, IL-5, and GM-CSF mRNA and secretion of the corresponding proteins.

Compared with controls, children with symptomatic asthma have higher percentages of activated peripheral blood T cells synthesising cytokines believed to regulate bronchial mucosal eosinophilic inflammation. Clinical improvement with increased inhaled GC therapy is associated with reduced T cell activation and cytokine mRNA expression.

We have measured the expression of messenger ribonucleic acid (RNA) (mRNA) encoding interleukin-5 (IL-5), IL-4, IL-2 and interferon-gamma (IFN gamma) in peripheral blood mononuclear cells (PBMC) from 10 patients with acute exacerbations of asthma and nine non-asthmatic controls. Measurements were repeated in seven of the asthmatics following 7 days of oral glucocorticoid therapy. Total RNA was extracted from the PBMC, reverse transcribed using oligo-(dT) primers and aliquots of the resulting complementary DNA (cDNA) amplified using the polymerase chain reaction (PCR) in the presence of cytokine-specific primers under non-saturating conditions. PCR products were quantified on a relative basis after Southern blotting and probing with radiolabelled internal oligonucleotide probes by computer assisted densitometry of blot autoradiographs. The relative amounts of IL-5 mRNA in PBMC from the asthmatic patients prior to glucocorticoid therapy were greater (P < 0.01) than those in PBMC from non-asthmatic controls. In contrast, there were no differences in the relative amounts of IL-4, IL-2 and IFN gamma mRNA. In the asthmatics, the relative amounts of IL-5 mRNA correlated with the peripheral blood eosinophil counts (P = 0.02). After oral glucocorticoid therapy of the asthmatics, lung function improved and the relative amounts of PBMC IL-5 mRNA were reduced (P = 0.04) and no longer differed from those in PBMC from non-asthmatic controls. Glucocorticoid therapy was not associated with significant changes in the relative amounts of PBMC IL-4, IL-2 and IFN gamma mRNA. PBMC from atopic subjects contained significantly greater quantities of IL-4 mRNA (P = 0.04) but not IL-5, IL-2 and IFN gamma mRNA compared with non-atopic subjects regardless of their asthmatic status. We conclude that PBMC of patients with acute exacerbations of asthma demonstrate elevated expression of mRNA encoding IL-5, but not IL-2, IL-4 and IFN gamma and that the clinical improvement associated with glucocorticoid therapy is associated with a reduction of IL-5 mRNA expression. We further conclude that elevated expression in PBMC of mRNA encoding IL-4 is a feature of atopy but not of asthma. These observations suggest that IL-5 synthesis by activated T-lymphocytes may be relevant to the pathogenesis of asthma, and that inhibition of this release by glucocorticoids may at least partly explain their therapeutic effect in this disease.

There now exists compelling evidence of a role for cell-mediated immunity in the pathogenesis of adult asthma, but little information is available as to what extent this process participates in the pathogenesis of childhood asthma. We hypothesised that asthma in children is associated with the activation of T-lymphocytes whose products regulate, at least in part, the mobilisation and recruitment of eosinophils and thereby disease severity. Our aims, therefore, were to compare the expression of activation markers, including CD45 isoforms, on peripheral blood T-lymphocytes from asthmatic and non-asthmatic, allergic control children matched for age and atopic status, and to attempt to correlate the percentages of activated T-lymphocytes in the asthmatics with the numbers of peripheral blood eosinophils and with disease severity. Seventeen children with moderate to severe chronic asthma were compared with 8 non-asthmatic, allergic children matched for age and atopic status. Expression of the activation markers CD25, HLA-DR and VLA-1 and the CD45 isoforms CD45RA and CD45RO on peripheral blood CD4 and CD8 T-lymphocytes was measured using dual fluorescence flow cytometry. Peripheral blood eosinophils were measured using an automated laser cytometer. Asthma severity was assessed by a symptom score, spirometry and measurement of histamine PC20. The absolute numbers of eosinophils in the peripheral blood of the asthmatics were elevated as compared to the non-asthmatic, allergic controls (p < 0.01), whereas the absolute numbers of both CD4+ and CD8+ T-lymphocytes were not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)