Reduced B cell HLA-DR expression and natural killer cell counts in patients prone to sepsis after injury

Objective: To examine the influence of natural killer (NK) cells and HLA-DR molecules on B cells in the development of severe sepsis after injury. Design: Prospective study. Setting: Medical school, Germany. Subjects: 46 severely injured (Injury Severity Score >16) patients. Interventions: Blood samples were taken immediately after admission and subsequently for 14 days. Main outcome measures: HLA-DR expression on B cells and counts of B and NK cells measured by how cytometry, and morphological estimation of large granular lymphocytes by microscopy. Results: HLA-DR expression on circulating B cells was significantly reduced from days 6-14 after admission in 13 patients with subsequent severe sepsis compared with 33 patients who did not develop sepsis. In septic patients NK cell counts were significantly decreased from day 4 onwards (p < 0.05). CD16+/CD56+ cells correlated with the morphology of large granular lymphocytes. Conclusion: In severely injured patients reduced counts of NK cells and HLA-DR molecules on B lymphocytes seem to be part of an immune deviation that is associated with the development of severe sepsis.