CCL3L1 protein did not affect IL-6 expression, but significantly up-regulated IL-10 expression in the allergic response

Background: Previously, we found that the mean copy number of CCL3L1 in patients with asthma was significantly lower than that of control subjects (3.13vs 3.75, p=0.001). We Investigate its possible molecular mechanism using a human monocytic cell line stimulated with house dust mite extract.

Method: The THP-1 human monocytic cells were stimulated with various concentrations of HDM extract. After stimulation assay-on-demand gene expression products(Applied Biosystems) were used to evaluate mRNA expression of CCL3L1 (Hs 00609691_ml), IlL-6 (Hs00174131_ml), and IL-10 (Hs00961622_ml) levels as measurement of mRNA levels by real time PCR.

Results: Treatment of THP-1 cells with various concentration of HDM extract induced marked up- regulation of the expression of cytokines IL-10 and IL-6, which indicated that allergic responses were efficiently induced.  Recombinant CCL3L1 protein had no effect on cytokine expression of THP-1 Cells in absence of HDM extract stimulation. In the presence of HDM extract(10 ug/ml) stimulation, CCL3L1 protein significantly  up-regulated  IL-10 expression (Ratio to ng/ml CCL3L1) dose-dependantly( 0 ug/ml CCL3L1 + 0.3;12.4, 10 ug/ml CCL3L1; 15.8+ 1.1, 50 ug/ml CCL3L1; 16.8+ 0.3, 100 ug/ml CCL3L1; 18.0+ 0.8, (p>.05), but did not affect IL-6 expression (p>.05).

Conclusion: The significantly elevated asthma risk in subjects with a low copy number of the CCL3L1 gene, which may be down-regulating IL-10 expression, not IL-6 expressiion.