Standardized measurement of HLA-DR expression on monocytes. (A) Monocytes are sorted according to their structure (SSC) and CD14 positivity. Among gated monocytes, the HLA-DR median fluorescence intensity (MFI) is measured and then (B) converted to the number of anti-HLA-DR antibodies bound per monocyte (Ab/c). FSC, forward scattered; MFI, median fluorescence intensity; SSC, side scattered.