Egypt J Pediatr Allergy Immunol 2005; 3(1): 20-31. Original article Plasma macrophage-derived chemokine (CCL22) and its receptor CCR4 on peripheral blood T lymphocytes of asthmatic children Background: The macrophage-derived chemokine (MDC/CCL22) acts on Mohamed H. Ezzat, CC chemokine receptor-4 (CCR4) to direct trafficking and recruitment of T Karim Y. Shaheen*. helper-2 (TH2) cells into sites of allergic inflammation. It was previously found overexpressed in lesional samples from adult asthmatics. Objective: This study is aimed to investigate the participation of CCR4/MDC axis in the development of TH2-dominated allergen-induced From the Departments childhood asthma in relation to disease activity, attack severity, and of Pediatrics and response to therapy, and to outline its value in differentiating atopic asthma Clinical Pathology*, from infection-associated airway reactivity. Faculty of Medicine, Methods: Proportion of CCR4-expressing peripheral blood T lymphocytes Ain Shams University, + (CCR4 PBTL%) were purified and quantitated by negative selection from Cairo, Egypt. peripheral blood mononuclear cells by flow cytometry, and the concentration of MDC in plasma was measured by ELISA in 32 children with atopic asthma (during exacerbation and remission), as well as in 12 children with acute lower respiratory tract infections (ALRTI), and 20 healthy children serving as controls. Results: The mean plasma MDC level (925±471.5 pg/ml) and CCR4+PBTL% (55.3±23.6%) were significantly higher in asthmatic children during acute attacks in comparison to children with ALRTI (109±27.3 pg/ml and 27.6±7.5%) and healthy controls (99.6±25.6 pg/ml and 24.2±4.1%). Both values decreased significantly after subsidence of attacks (502±284.3 pg/ml and 32.5±10.5%) although remained higher than the other 2 groups which were actually comparable in terms of MDC and CCR4%. MDC and CCR4% values were higher among children with acute severe than mild or moderate asthma exacerbations, and in persistent than intermittent cases during stability. Positive correlations could be elicited between both markers during exacerbation or stability, and between the exacerbation level of each and its corresponding value during remission. Corticosteroid- treated patients had the highest expression of both markers when relation to therapy was studied. Conclusion: Our findings reinforce the concept that up regulation of CCR4/MDC axis is implicated in the pathogenesis of pediatric atopic Correspondence: asthma and may represent a useful biomarker of monitoring allergic Mohamed Hesham inflammation and response to therapy. Neutralization and manipulation of Ezzat CCR4-expressing T cells, as well as MDC antagonism, may represent an 25 El-Sebak Street adjuvant in the treatment of severe allergic disorders. Cairo 11451, Egypt E-mail: ezzatmhm Key words: MDC; CCR4; T-lymphocytes; flowcytometry; asthma; children @hotmail.com INTRODUCTION subsets express restricted chemokine receptors. For Chemokines and chemokine receptors provide example, TH1 cells express the chemokine directional cues for leukocyte migration and receptors CXCR3 and CCR5, while CCR4, CCR8, concomitantly induce the recruitment of T cells into and CCR9 are found on TH2 cells.1, 2 the sites of inflammation. This process is CCR4 is a receptor that binds 2 chemokines; particularly important in atopic diseases such as CCL17/TARC (Thymus and Activation-Regulated bronchial asthma. Initial studies in this area have Chemokine), and CCL22/MDC (Macrophage- emphasized that chemokine receptor expression is Derived Chemokine). The receptor was originally tightly regulated on TH cells, and that TH cell isolated from a basophilic cell line and shown to be 20 Ezzat and Shaheen. expressed on a subpopulation of peripheral blood into 3 main groups: 32 children with allergic lymphocytes, thymocytes, mature dendritic cells bronchial asthma (group I), 12 children with acute and recently on blood platelets.3 Current evidence lower respiratory tract infections (group II), and 20 suggests that CCR4 expression is associated with healthy children not expressing airway disease TH-2 responses. Activation of T cells through their (group III) serving as controls An informed consent T-cell receptor can induce elevated CCR4 levels, was obtained from the parents or caregivers of each which can last up to two days.4 child before enrollment. Chemokines basically have been divided into Group (I): It comprised 32 children enrolled from two main families, CXC and CC chemokines, based the Pediatric Allergy and Immunology Unit of Ain on the sequence homology and the position of the Shams University Children’s Hospital while first two cysteine residues. CXC chemokines are presenting with an acute asthmatic exacerbation. typically chemotactic for neutrophils, whereas CC They were followed-up until complete clinical chemokines attract and activate monocytes and subsidence of the attack and then re-evaluated. lymphocytes.5 MDC or CCL22 is a novel human 8 Their ages ranged between 3 and 12 years (mean ± kDa CC chemokine. It was originally cloned from SD = 7.6 ± 2.3 years), and they comprised 20 boys human monocyte-derived macrophage cDNA (62.5%) and 12 (37.5%) girls. The asthma clones. It is composed of 69 amino acid residues exacerbations were triggered by exposure to and has been termed MDC because it appears to be allergens (food, animal allergens or both) in 20 synthesized specifically by cells of macrophage children and upper respiratory tract infections in 3 lineage.6 Unlike most other CC chemokines, MDC children. In 9 children, the triggering agent was not is clustered on chromosome 16q13. It was clear. Thirteen children (41%) presented with acute previously known as STCP-1 (stimulated T cell severe asthma, 9 (28%) with moderate severe chemotactic protein-1). It has the 4 cysteine motif asthma, and 10 (31%) had exacerbations of mild and other highly conserved residues characteristic severity based on clinical data and peak expiratory of CC chemokines, but it shares less than 35% flowmetry (PEFR).11, 12 Sixteen patients (50%) had sequence identity with other human chemokines, radiological evidence of hyperinflation and especially TARC being its closest known human increased bronchovascular markings. Based on the relative.7, 8 criteria of asthma grading, the clinical severity of CCR4/MDC axis plays an important role in the the recruited asthmatics during stability were long-term recruitment of TH2 cells into the classified into intermittent asthma (IA) in 17 inflammatory sites and the regulation of TH2- children (53%) and persistent asthma (PA) in 15 related immune responses. CCR4/MDC axis has children (47%) according to the Global Initiative been directly associated with an asthma diagnosis for Asthma (GINA) guidelines.13 Asthmatic and found to be inversely related to lung function as children were further subdivided according to measured by FEV1.9 The established in vivo intake of inhaled corticosteroids into those on significance of distinct CCR4 expression on TH2 therapy (n=14; 44%) (mean dose = 250 ± 50µg and cells, and chemotactic and activating effects of a mean duration of 8.2 ± 6.4 months and those who MDC on TH2 cells and the association of TH2 cells were not (n=18; 56%). The latter group was on one with asthma activity and severity suggest that this or more of the following medications: inhaled 10 axis is pivotal in asthma. The current study is sodium cromoglycate, oral/inhaled β2 agonists, or therefore aimed to elucidate the role of CCR4/MDC theophylline. axis in pediatric asthma by tracing and following up Group (II): It comprised 6 boys and 6 girls whose their expression during activity and in-between ages ranged from 4 to 11 years with a mean ± SD of attacks and to outline their relation to other 7 ± 1.4 years. They were enrolled after exclusion of parameters denoting disease activity, degree of a past, current or family history of allergic severity, and response to therapy. Also, to evaluate disorders, peripheral blood eosinophilia or elevated their discriminative value between allergic asthma serum total IgE for age.14 Detailed history taking, and infection-associated bronchospasm. This may clinical examination, and chest auscultation have an implication for new non-conventional lines findings as well as chest radiographs were of therapy. consistent with the diagnosis of bronchopneumonia in 4 patients, lobar pneumonia in 3 patients, METHODS bronchiectasis in 3 patients (secondary to cystic This follow-up, case-control study was conducted fibrosis), and chronic bronchitis in 2 patients. over a period of 1 year from March 2004 to the end Children with bronchiectasis and chronic bronchitis of February 2005. It comprised 64 children divided 21 MDC (CCL22) / CCR4 axis in asthma were sampled during an acute exacerbation of and any MDC present was bound by the infection. immobilized antibody. After washing away any Group (III): It comprised 11 boys (55%) and 9 unbound substances, a horseradish peroxidase- girls (45%) whose ages ranged from 5 to 12 years linked monoclonal antibody specific for MDC was with a mean ± SD of 8 ± 2.2 years. They were added to the wells. Following a wash to remove any enrolled after exclusion of a personal and family unbound antibody-enzyme reagent, a substrate history of allergic disorders, peripheral blood solution of hydrogen peroxide-tetramethylbenzidine eosinophilia or elevated serum total IgE for age.14 was added to the wells and color developed in Patients or control subjects with clinical or proportion