Neutrophils express membrane Orai1. Isolated mouse and human PMNs, or 2-day differentiated HL-60 were assessed for RNA, DNA, or protein expression. (A) Protein expression levels were measured from the average mean fluorescence intensity (MFI) of paired flow cytometry samples of HL-60 cells transfected with negative control or Orai1-specific siRNA (n = 10) and PMNs (n = 4). Background fluorescence resulting from nonspecific antibody binding was measured by analyzing cells treated with a blocking decoy peptide against which the Orai1 antibody was originally raised. (B) Relative expression levels of Orai1 mRNA compared with RPL mRNA were measured for siRNA-transfected, control siRNA-transfected, or mock-transfected HL-60 cells by quantitative PCR. Data expressed as Orail mRNA copy number relative to RPL after PCR amplification. (C) Relative genomic DNA expression of Orai1 in WT versus Orai1−/+ mice measured by electrophoresis of amplified DNA from mouse tissues. Bars represent average densitometry measurements from 18 Orai1−/+ and 6 littermate WT mice ± SE. (D) Orai1 protein expression measured from the average MFI of paired cytometric measurements in WT and Orai1+/− mouse PMNs (n = 3). *P < .05; ***P < .001.