Cell surface down regulation of CCR5 or CXCR4 coreceptors in siRNA transfected GHOST-R3/X4/R5 cells. GHOST-R3/X4/R5 cells that constitutively express CCR5 and CXCR4 coreceptors were transfected with control RFP, CCR5 or CXCR4 siRNA constructs. RFP expressing transgenic cells were FACS sorted and cultured. To determine the down regulation of respective coreceptors, the cells were stained with respective FITC tagged antibodies and FACS analyzed. The down regulation of CCR5 coreceptor (Panel A) was determined by comparing CCR5 levels in untransfected (A1), control RFP transfected (A2) and CCR5 siRNA transfected (A3) cells. The CXCR4 coreceptor down regulation is shown by comparing CXCR4 levels in untransfected (B1), control RFP transfected (B2) and CXCR4 siRNA transfected (B3) cells. The percent down regulation of CCR5 (A4) or CXCR4 (B4) coreceptors is also indicated.