Polymerase chain reaction quantification of cytokine messenger RNA expression in peripheral blood mononuclear cells of patients with acute exacerbations of asthma: effect of glucocorticoid therapy.
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.
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Department of Allergy and Clinical Immunology, National Heart and Lung Institute, London, UK.
Gemou-Engesaeth
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Kay
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Corrigan
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D000199:Actins / Q000235:genetics; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001249:Asthma / Q000097:blood* / Q000188:drug therapy*; D001483:Base Sequence; D002648:Child; D016207:Cytokines / Q000235:genetics*; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use*; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000737:chemistry / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000097:blood*; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D000199:Actins; D016207:Cytokines; D018076:DNA, Complementary; D005938:Glucocorticoids; D012333:RNA, Messenger