Activated peripheral blood CD4 and CD8 T‐lymphocytes in child asthma: correlation with eosinophilia and disease severity

Abstract

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)

Expression of Activation Markers and Cytokine mRNA by Peripheral Blood CD4 and CD8 T Cells in Atopic and Nonatopic Childhood Asthma: Effect of Inhaled Glucocorticoid Therapy

“…The percentages of CD4 and CD8 T cells staining positively for activation markers were corrected by subtracting the numbers of cells stained with PE-conjugated, isotype-matched control antibodies. 15,16 …”

“…Before lung function testing, 10 to 15 mL of peripheral venous blood was collected into heparin for isolation of mononuclear cells and full blood count, and serum isolated for total (Unicap, Pharmacia) and specific IgE measurements. Severity of symptoms was graded as done previously, 15,16 according to the method of Aas, 25 which was shown in a previous study 26 to correlate with eosinophil infiltration of the bronchial mucosa.…”

“…15,16 In brief, inhaled glucocorticoid therapy was initiated or increased if asthma severity was not considered mild. Mild asthma was defined as absence of exercise and nocturnal symptoms, no significant loss of school time, requirement for no more than 3 doses of inhaled ␤2-agonists weekly, and lung function test (FEV1) above 85% of the predicted values, as described previously.…”

“…Flow cytometry was performed by dual fluorescent staining as previously described, 15,16 except that peripheral blood T cells were stained directly in whole blood. Fluorochrome-IgG murine monoclonal antibodies against the following cell markers were used: fluoroscein isothiocyanate (FITC)-labeled anti-CD4 and anti-CD8 (DAKO A/S, Glostrup, Denmark); phycoerythrin (PE)-labeled anti-CD25 (DAKO A/S), anti-HLA-DR (Becton Dickinson, San Jose, CA), anti-CD45-RA and anti-CD45-RO (DAKO A/S,) and IgG1/ IgG2a irrelevant control antibodies coupled to FITC and PE, respectively, (DAKO AS).…”

“…Fortunately, the studies on the properties of peripheral blood T cells in adult asthma cited above suggest that the properties of these cells reflect those of cells in the bronchial mucosa, owing perhaps to a "spillover" or recirculation of these cells into the peripheral circulation. 4 -9,13,14 We have used this observation in previous studies to demonstrate that in atopic child asthmatics as compared with controls matched for age and atopic status, elevated percentages of both CD4 and CD8 peripheral blood T cells expressed activation markers, 15 whereas elevated percentages of unfractionated peripheral blood mononuclear cells expressed mRNA encoding eosinophil-active cytokines including IL-5 and IL-4. 16 First, we wanted to extend these studies to examine cytokine production by both CD4 and CD8 T cells in child asthmatics.…”