Role of regulatory CD4+CD25+ Foxp3 T cells in bronchial asthma in Egyptian children.

CD4+CD25+high Foxp3 regulatory T (Treg) cells are known to play a key role in balancing immune response to maintain peripheral tolerance against harmless antigens or allergens. Defective immunological suppression by CD4+CD25+high Foxp3 Treg cells can be a cause of the inflammation that leads to an allergic condition such as asthma. The aims of the study are to (1) determine CD4+CD25+high Foxp3 Treg cells frequency in the peripheral blood of children with and without asthma; and (2) investigate the association between CD4+CD25+high Foxp3 Treg cells frequency with disease severity and corticosteroid therapy. Sixty asthmatic children with varying disease severity (20 mild, 20 moderate and 20 severe) were enrolled in the study. Severe asthmatic children were further subdivided into two groups, one on corticosteroid therapy and the other was not on corticosteroid. Twenty age and sex matched healthy children were enrolled as controls. Number of circulating CD4+CD25+high Foxp3 Tregs were measured using flow cytometry. Our finding demonstrates that children with asthma had a significant decrease of CD4+CD25high Foxp3 Treg cells and Tregs/T effectors ratio in peripheral blood compared to children without asthma. Patients with moderate asthma demonstrated lower frequency of CD4+CD25+high Foxp3 Treg cells compared to mild and severe asthmatic patients. Those on corticosteroid therapy revealed significant increase in CD4+CD25+high Foxp3 Treg cells and decrease in T effectors. It is concluded that asthmatic children have decreased number of CD4+CD25+high Foxp3 Treg cells leading to increase in effectors cells which mediate inflammation in the airways. Corticosteroid therapy plays a role in elevating number of CD4+CD25+high Foxp3 Treg cells and maintaining its suppressor function.