HLA-DR expression in septic shock patients and healthy controls. (a) Cell surface expression of HLA-DR measured by flow cytometry. A representative CD14 versus side-scattered light (SSC) dotplot and representative HLA-DR linear histograms gated on monocytes in one healthy volunteer and one septic patient (white histogram = isotype control). (b) Boxplot representations of mHLA-DR measurements by flow cytometry and quantitative reverse transcription (qRT)-PCR (white boxes, percentage of HLA-DR-expressing monocytes; dashed boxes, normalized ratio of HLA-DRA mRNA level relative to the housekeeping gene peptidylpropyl isomerase B) measured in whole blood or mononuclear cells from septic shock patients or healthy controls (n = 10). Values were measured at days 1 to 2 (D1-2, n = 7) and days 3 to 5 (D3-5, n = 10) for septic patients. Normal values: >90% for flow cytometry and 2 ± 0.3 for mRNA expression. Comparison versus healthy volunteers' (HV) values (means) performed using the Mann-Whitney U test with correction for the number of tests performed: *P < 0.025. mHLA-DR values expressed as the number of bound antibodies per cell (AB/c) were 15,985 ± 2,331 at D1-2 and 11,057 ± 2,691 at D3-5 in patients (>15,000 AB/c as indicative of immunocompetence ).