Copy number variation of CCL3L1 influences asthma risk by modulating IL-10 expression

► We compared the copy number of CCL3L1 gene in control and asthma subjects. ► Mean copy number was significantly lower in asthma than control subjects. ► Low copy number of ≤ 1 was associated with higher asthma risk and serum IgE level. ► High copy number of ≥ 5 was associated with decreased asthma risk. ► CCL3L1 protein up-regulated IL-10 expression in house dust mite-stimulated monocytes.