Serum 25-hydroxyvitamin D and CD4+CD25(+high) FoxP3+ Regulatory T cell as Predictors of Severity of Bronchial Asthma in Children.

Bronchial asthma (BA) is one of the common chronic diseases of childhood. Vitamin D deficiency has been associated with BA. Suppressor regulatory T cells (Treg) are important for the induction, maintenance of immunological tolerance to allergens. This study assessed serum 25-hydroxyvitamin D (vitamin D) and the percentages of CD4+CD25+(high) Foxp3+ Treg, in peripheral blood, as predictors of asthma severity and level of clinical control. The study enrolled 72 children divided equally between asthmatic children (AC) and age and sex matched controls. Diagnostic criteria and level of asthma severity followed the Global Initiative for Asthma guidelines. Serum vitamin D was determined by an immunoassay and the percentages of CD4+CD25+ig Foxp3+ Treg by flow cytometry. Serum vitamin D level and percentage of CD4+CD25+(high) Treg were lower in AC compared to controls (P < 0.001) whereas Fox p3 expression was higher in AC compared to controls, P < 0.001. Serum vitamin D levels were lower in severe asthma compared to mild and moderate forms (P = 0.008) and in uncontrolled attacks compared to partially or completely controlled children. No difference in percentage of Treg in relation to asthma severity and clinical control was observed. Since AC has decreased serum vitamin D with inverse relationship between its levels and asthma severity, we conclude that it can be used to predict severity of asthma.