The samples of PM2.5 were collected by a particulate sampler (TH-150C, Wuhan Tianhong Instruments Co. Ltd., Wuhan, China) in residential area of Beijing, China, from 1 December 2014 to 20 February 2015. Filters were cut into 1–2 cm2 squares. The filter squares were agitated in ultrapure water with an ultrasonic shaker for 20 min 3 times. The solution was filtered through 8 layers of gauze and centrifuged at 12,000 rpm for 20 min. The sediment was collected by a vacuum freeze drier (FDU-1100, Tokyo Rikakikai Co. Ltd., Tokyo, Japan). The dry PM2.5 powder was diluted in sterile phosphate-buffered saline (PBS) (0.01 M, pH 7.4) at a concentration of 15 mg/mL and kept at −20 °C before experiments. An extra control sample from unexposed filters was processed identically. Morphology of PM2.5 particles was observed with a scanning electron microscope (SEM) (JSM-5600LV, Jeol Ltd., Tokyo, Japan).
Quercetin (Sigma products, purity ≥ 95.0%) was respectively dissolved in 0.15% CMCS at a concentration of 10, 20, and 40 mg/mL. IL-2, IL-6, IL-8, TNF-α, and HO-1 enzyme-linked immunosorbent assay (ELISA) kit were purchased from Freemore (Beijing, China). FITC-anti-CD3, PE/Cy7-anti-CD8, Brilliant Violet 421-anti-CD4, PE-anti-CD5, APC-anti-CD19, and red blood cell lysis buffer were purchased from BioLegend (San Diego, CA, USA).
Quercetin (Sigma products, purity ≥ 95.0%) was respectively dissolved in 0.15% CMCS at a concentration of 10, 20, and 40 mg/mL. IL-2, IL-6, IL-8, TNF-α, and HO-1 enzyme-linked immunosorbent assay (ELISA) kit were purchased from Freemore (Beijing, China). FITC-anti-CD3, PE/Cy7-anti-CD8, Brilliant Violet 421-anti-CD4, PE-anti-CD5, APC-anti-CD19, and red blood cell lysis buffer were purchased from BioLegend (San Diego, CA, USA).